Weed control in alfalfa (Medicago sativa L.) grown for seed
by Mark Edward Stannard
A thesis submitted in partial fulfillment of the requirements for the degree of Master of Science in
Agronomy
Montana State University
© Copyright by Mark Edward Stannard (1987)
Abstract:
Hexazinone is a broad spectrum herbicide that was popular with the alfalfa (Medicago sativa L.) seed
producers in Montana. Although hexazinone was a valuable herbicide, there were frequent reports of
alfalfa injury from 1982 to 1984. Several factors were investigated to determine possible causes of
injury. Three factors implicated in most cases were low soil organic matter, application of hexainone to
nondormant alfalfa, and application of hexazinone to alfalfa which endures stress conditions later that
growing season.
Alfalfa seedlings are very sensitive to soil residues of chlorsulfuron. Approximately.20 million alfalfa
seeds were sown into soil previously treated with 35 g ai/ha. chlorsulfuron. This mass selection
technique produced 15 healthy alfalfa plants each representing a line. Each line was cloned and tested
for tolerance to chlorsulfuron applied as a foliar spray and as a soil drench. Seven lines were tolerant to
foliar application and six were tolerant to soil drench. Acetolactate synthase from two lines was more
tolerant to chlorsulfuron than control lines.
A weed survey was conducted in 36 and 23 certified alfalfa seed production fields in 1985 and 1986,
respectively. Fifty-six and 35 weed species were identified in fields in 1985 and 1986, respectively.
Eight of the 10 most frequently occurring weeds of 1985 were among the 10 most frequently occurring
weeds of 1986. Chemical weed control was the most common method of weed control. Canada thistle (
Cirsium arvense L.) was perceived to be the most troublesome weed by producers. WEED CONTROL IN ALFALFA (Medlcago satIva L .)
GROWN FOR SEED
by
Mark Edwin Stannard
A thesis submitted in partial fulfillment
of the requirements for the degree
of
Master of Science
in
Agronomy
MONTANA STATE UNIVERSITY
Bozeman, Montana
August 1987
MAIN LIB.
N31S
c2^
ii
APPROVAL
of a thesis submitted by
Mark E . Stannard
This thesis has been read by each member of the thesis
committee and has been found to be satisfactory regarding
content, English usage, format, citations, bibliographic
style, and consistency, and is ready for submission to the
College of Graduate Studies.
S ' 'Sn
Chairperson, Graduate Committee
Date
Approval for the Major Department
2 V //ff
Date
Head, Major Department
Approval for the College of Graduate Studies
9-Z/-/ 7
Date
Graduate Dean
iii
STATEMENT OF PERMISSION TO USE
In presenting this thesis in partial fulfillment of the
requirements for a master's degree at Montana State
University, I agree that the Library shall make it available
to borrowers under rules of the Library.
Brief quotations
from this thesis are allowable without special permission,
provided that accurate acknowledgment of source is made.
Permission for extensive quotation from or reproduction
of this thesis may be granted by my major professor, or in
his absence, by the Director of Libraries when, in the
opinion of either, the proposed use of the material is for
scholarly purposes.
Any copying or use of the material in
this thesis for financial gain shall not be allowed without
my written permission.
Signature
Date
V
ACKNOWLEDGEMENTS
I
thank my advisor, Dr. Pete Fay, for the help and
encouragement he provided during my education.
I
also appreciate the assistance and direction given by
other members of my committee, Jim Nelson and Ray
Ditterline.
I would also like to thank the people in the weeds
group, Mike Foley, Gary Fellows, Dan Burkhart, Scott Nissen,
Lee Coble, Ed Davis, Eric Gallandt, Gary Kagel, and Joe
DiTomaso, for their help, support and friendship.
Lastly, I would like to thank my parents for supporting
my endeavors, and my wife, Dennise, for her patience and
support.
vi
TABLE OF CONTENTS
Page
A P P R O V A L .............................................
STATEMENT OF PERMISSION TO USE
ii
'.....................
ill
V I T A ................................................
iv
ACKNOWLEDGMENTS
TABLE OF CONTENTS
....................................
..................................
LIST OF T A B L E S .......................
LIST OF F I G U R E S ......................................
A B S T R A C T ..............
v
vi
viii
xii
xiii
Chapter
1
2
LITERATURE REVIEW
...........................
I
Hexazinone
.............................
ChlorsuIfuron ...........................
Acetolactate Synthase ...................
Selecting Plants for Herbicide
R e s i s t a n c e .............................
Weed S u r v e y s ...........................
I
6
11
THE PROBABLE CAUSES OF HEXAZINONE INJURY
TO ALFALFA
................... .. ,........
Introduction
.■.........................
Methods and Materials ...................
Results and Discussion
.................
16
21
23
23
24
27
Chapter
3
4
Pag e
SELECTION OF ALFALFA {Medicago sativa L .)
PLANTS FOR RESISTANCE.TO CHLORSULFURON
. .
34
Introduction
.............................
Methods and Materials
...........;
. .
Results and D i s c u s s i o n ............. .. .
34
35
39
A WEED SURVEY OF CERTIFIED ALFALFA SEED
PRODUCTION FIELDS OF MONTANA.
.............
BIBLIOGRAPHY
45
Introduction
.............................
Methods and Materials
.................
Results and Discussion
...................
45
46
52
.........................................
97
A P P E N D I C E S .............................................
105
Appendix A - 1985 Alfalfa herbicide
demonstration plots located at
Laurel, Malta, and Miles C i t y ..............
106
Appendix B - Herbicide guide f o r ,
alfalfa and other forage
legumes
115
viii
LIST OF TABLES
Table
1
2
3
4
5
6
7
Page
Soil characteristics and hexazinone
application conditions for the
hexazinone research plots at Laurel
and Malta, MT (1986)
The 15 most frequently occurring
weed species in certified alfalfa seed
fields in Montana in 1985 and 1986 . . . .
27
28
Effect of herbicide treatments applied to the
established alfalfa in 1987 which had been
previously treated with 1.1 kg/ha hexazinone
on March 3 and 8, 1986 .......................
30
Comparison of acetolactate synthase (ALS)
Iq q values for Ladak 65 and Apollo II
and 8 chlorsulfuron tolerant alfalfa lines .
42
Biomass produced by Ladak 65 and Apollo II and
alfalfa lines selected for chlorsulfuron
tolerance 2I days after clipping in the
greenhouse. ............. .. . ....... . . . .
42
Frequency, occurrence, density, and relative
abundance of 56 weed species common to
alfalfa seed fields surveyed in 1985
...
53
Weed density, number of species, moisture
source■, seeding method, and weed
control practices used in 36 alfalfa seed
fields surveyed in 1985
. . . . . . . . . .
58
ix
Table
8
9
10
11
12
13
14
15
16
Page
Frequency, occurrence, density, and relative
abundance of 35 weed species common to
alfalfa seed fields surveyed in 1986. . . .
59
Weed density, number of species, moisture
source, seeding method, and weed
control practices used in 23 alfalfa
seed fields surveyed in 1986 . . . . . . .
62
The most frequently occurring weeds species
infesting alfalfa seed fields where
cultural weed control practices were
used
............
. . . . . . . . . . . .
64
The most frequently occurring weed species
infesting alfalfa seed fields where
chemical control practices were used
...
65
Frequency, occurrence, density, and relative
abundance of weed species common to new
seedings of alfalfa surveyed in 1985
. . .
67
Frequency, occurrence, density, and relative
abundance of weed species common to
dryland alfalfa seed fields surveyed in
1985 and 1986 . i ............................
70
Frequency, occurrence, density, and relative
abundance of weed species common to
irrigated alfalfa seed fields surveyed
in 1985 and 1986
7
Frequency, occurrence, density, and relative
abundance of weed species common to
alfalfa seed fields surveyed in the upper
Yellowstone river alfalfa.seed
production region ............................
Frequency, occurrence, density, and relative
abundance of weed species common to
alfalfa seed fields surveyed in the Milk
river alfalfa seed production region
; . .
81
84
X
Table
17
18
19
20
21
22
23
24
25
26
27
Page
Frequency, occurrence, density, and relative
abundance of weed species common to
alfalfa seed fields surveyed in the lower
Yellowstone river alfalfa seed
production region ................. ..
88
Frequency, occurrence, density, and relative
abundance of weed species common to
alfalfa seed fields surveyed located in
regions other.than the Milk river, lower
and upper Yellowstone river alfalfa seed
production regions. . . . . . .
91
Ten most effective weed control practices
of alfalfa seed fields surveyed in 1985 . .
95
Ten most effective weed control practices
of alfalfa.seed fields surveyedin 1986 . .
95
Participants of the ,1986 herbicide
demonstration tours and their respective
presentations ................. . . . . . .
108
Testing herbicides applied early in the spring
to dormant alfalfa grown for seed. Knudsen
Farms. Malta, MT . . . . . . . . . . . . . ..
109
Testing herbicides applied early in the spring
to dormant alfalfa grown for seed.
Knudsen
Farms. Malta, M T ........... ................
HO
Testing herbicides applied late in the fall
to dormant alfalfa grown for seed. Gary
Wiltse river farm. Miles City, M T ..........
Ill
Testing herbicides applied late in the fall
to dormant alfalfa grown for seed. Gary
Wiltse river farm. Miles City, M T ..........
112
Testing herbicides applied early in the spring
to dormant alfalfa grown for seed. John
Wold farm. Laurel, MT
. . . ...............
113
Testing herbicides applied early in the spring
to dormant alfalfa grown for seed. John
Wold farm. Laurel, MT
.
114
xi
Table
28
Page
Weed response to herbicides applied to
alfalfa and other forage legumes
..........
/
127
xii
LIST OF FIGURES
Figure
Page
1
Structure of hexazinone ..............
2
Hexazinone metabolites
3.
Molecular structure of chlorsulfuron
4
Percent organic matter content of soils in
fields with and without hexazinone
injury to alfalfa . . . . . . .
..........
5
6
7
8
9
10
11
...
2
.....................
3
... .
7
32
Percent sand and clay content of soils in
fields with and without hexazinone
injury to alfalfa . ...................
Tolerance of alfalfa plants to 35 g/ha
chlorsulfuron applied as a foliar
spray and as a soil drench
. . . . . . . .
32
40
The activity of acetolactate synthase
(ALS) from Ladak 65 alfalfa at 8
concentrations of chlorsulfuron .............
43
Counties and locations of alfalfa seed
fields surveyed in 1985 .....................
47
Counties and locations of alfalfa seed
fields surveyed in 1986 . . . . . . . . . .
48
Counties of the Milk river, lower
Yellowstone river, and upper
Yellowstone river alfalfa seed
production regions of M o n t a n a ...............
Most troublesome weeds of alfalfa seed
fields as perceived by the producers
79
96
ABSTRACT
Hexazinone is a broad spectrum herbicide that was
popular with the alfalfa {Medicago sativa L .) seed producers
in Montana. Although hexazinone was a valuable herbicide,
there were frequent reports of alfalfa injury from 1982 to
1984. Several factors were investigated to determine
possible causes of injury. Three factors implicated in most
cases were low soil organic matter, application of hexainone
to nondormant alfalfa, and application of hexazinone to
alfalfa which endures stress conditions later that growing
season.
Alfalfa seedlings are very sensitive to soil residues
of chlorsulfuron. Approximately.2Q million alfalfa seeds
were sown into soil previously treated with 35 g a i / h a .
chlorsulfuron.
This mass selection technique produced 15
healthy alfalfa plants each representing a line.
Each line
was cloned and tested for tolerance to chlorsulfuron applied
as a foliar spray and as a soil drench.
Seven lines were
tolerant to foliar application and six were tolerant to soil
drench.
Acetolactate synthase from two lines was more
tolerant to chlorsulfuron than control lines.
A weed survey was conducted in 36 and 23 certified
alfalfa seed production fields in 1985 and 1986,
respectively. Fifty-six and 35 weed species were identified
in fields in 1985 and 1986, respectively.
Eight of the 10
most frequently occurring weeds of 1985 were among the 10
most frequently occurring weeds of 1986. Chemical weed
control was the most common method of weed control. Canada
thistle ( Cirsium arvense L .) was perceived to be the most
troublesome weed by producers.
CHAPTER I
LITERATURE REVIEW
Hexazinone
Hexazinone, [3-CYclohexyl-6-dimethylamino-l-methyl1,3,5-triazine-2,4(IHf3H)-dione], is a broad spectrum
herbicide developed by the E.I. DuPont Company (67).
It was
first labeled for noncropland use in 1975 and is marketed
under the trade name of "Velpar" in liquid, dry flowable and
pellet formulations (40). Hernandez et a l . (30) described
the herbicidal properties of hexazinone in 1974.
Hexazinone is the only tr.iazine herbicide that has a
cyclohexyl ring attached to the 3 position of the triazine
ring (Figure I) (50,57).
The solubility of hexazinone in water is 33,000 ppm at
25 C , the most water soluble triazine herbicide (7,8,33,40).
Solubility decreases approximately 50% when water
temperature is decreased 20 C (3).
Because of its high
water solubility and relatively low soil adsorption
properties, hexazinone is very mobile in soil and leaches
readily.
Bouchard et a l . (8) reported that 90% of the
hexazinone applied to soil columns was leached below the top
10 cm of a gravelly fine-sandy loam soil 42 days after
2
application.
0
Figure I.
Structure of hexazinone.
Hexazinone is readily adsorbed by soil organic matter,
especially organic matter that has undergone little
decomposition (7).
Hexazinone has less affinity for soil
particles than for organic matter.
Rhodes (59) reported the
soil thin layer chromatography (TLC) Rf values for
hexazinone, terbacil [3-tert-butyl-5-chloro-6-methyluracil],
and diuron [3-(3,4-dichlorophenyl)-I ,I-dimethyIur e a ] are
0.68, 0.47, and 0.20 respectively on a
soil.
Flanagan silt loam
Hexazinone is classified as a Class 4 mobile
herbicide (59).
Hexazinone dissolved in distilled water is stable in
light at temperatures up to 37 C (58).
However, the
addition of stream sediment or riboflavin to distilled water
increased the decomposition rate of hexazinone three to
seven fold (58).
Rhodes (58) stated that riboflavin and
stream sediments acted as photoinitiators which aided in the
3
photodecomposition of hexazinone.
Microbial degradation is the primary means of
decomposition of hexazinone (40,69).
The primary
degradation products of hexazinone are demethylated and
hydroxylated triazine rings, and hyroxylated cyclohexyl
rings (57,58,59,67),
0
0
0
( sV n ^ nh
o = \> - o
H0 ”
(Figure 2).
(S )-N ^ N
O = ^ n J l N ( C H 3 )2
0
( sV n ^ n
( sV n ' S j
O = ^ n J l NHCH3
O=Jx n Jl NH2
CH 3
H
CH3
CH5
D
H
B
F
0
0
0
N
NH
ho
V
sV
n^ n
Ho Y
O =1^ n J - N (C H 3 )2
0 = ^ 0
sV
n^ n
O=Jx.., J fc- N H C H 3
'
(
0
s)
- na n
0 =Jxi n J 1- N H C H
CH3
CH3
CH3
H
E
A
C
G
Figure 2. Hexazinone metabolites.
The mode of action of hexazinone is not completely
understood (67).
However, like the other triazines,
hexazinone is a strong inhibitor of photosynthesis in
susceptible plants.
The mode of action of triazines such as
atrazine (6-chloro-N-ethyl-N1-(I-methyIethyl)- 1 ,3,5triazine-2,4-diamine) and metribuzin ((4-amino-6-(1,1-
4
dimethyIethyl)-3-(methylthio)-l,2,4-triazin-5(4H)-one) is
the inhibition of electron.transport at the Hill reaction
(9,45,65).
The mode of action of hexazinone is probably
similar.
Hexazinone reduced the level of RNA synthesis in
isolated soybean cells which may be a secondary effect
caused by a reduction in photosynthesis (28). Hexazinone has
little activity on lipid synthesis (28).
The selectivity of
hexazinone is probably a result of metabolism by tolerant
plants (42,65).
McNeil (42) reported that intact hexazinone
in the leaves of loblolly pine (Pinus taeda L.), a tolerant
species, inhibited photosynthesis.
Some tolerance in
Loblolly pine may be accounted for by lack of translocation
of hexazinone to the site of action since hexazinone not
translocated out of the root system did not inhibit
photosynthesis.
Rhodes (59) studied the rate of disappearance of
hexazinone in soil.
He found the half life ranged from I to
6 months in soils in the northeast, midwest, and delta
regions which are characterized by relatively high
precipitation and long frost-free periods (59).
Richardson
and Parker (56) reported that no hexazinone was detected 7
weeks after application of 0.05 kg/ha in incubated moist
soil.
Rates of 0.15 and 0.45 kg/ha killed bioassay plants
38 weeks after spraying.
Rhodes (58,59) and Rhodes and Jewell (57) identified
5
eight metabolites of hexazinone in water and soil, and from
excretion samples from rats and fish.
Only metabolite B
(Figure 2) exhibited significant herbicidal activity
(66,67).
Sung (67) reported that metabolite B inhibited
photosynthesis of loblolly pine at rates comparable to field
rates of hexazinone.
Sung (67) reported that the dione and
nonsubstituted cyclohexyl ring are critical for herbicidal
activity.
Loblolly pine is tolerant to hexazinone at soil
application rates of 4 kg/ha (66).
Other species which exhibit tolerance to soil
applications of hexazinone are sugar cane (Saccharum
offieinarum L.), blue berries ( Vaccinium corymbosum L.),
rubber (Ficus spp.), oil palm (Elaeis guineensis J.), coffee
(Coffea spp.), tea (Camellia sinensis L.), pineapple (Ananas
comosus L.), post-emergence applications to onions (Allium
spp.), certain Pinus, Picea, and Abies; and alfalfa
(3,33,51,57,71,76).
)
Hexazinone must not be applied to the actively growing
foliage of many species tolerant to soil application.
Jenson (33) reported 40% injury when hexazinone was applied
to the foliage of actively growing blueberries.
Baron et
a l . (5) reported no correlation between 13 blueberry
cultivar types and injury.
They reported that soil organic
matter and cation exchange capacity were important factors
when determining blueberry tolerance to hexazinone.
Unfortunately, the cation exchange capacity of the soils
6
used by Baron et a l . was derived almost entirely from
organic matter since silt and clay content was very low.
Their conclusion about the importance of cation exchange
capacity, and not organic matter, as a regulating factor of
hexazinone tolerance may not be correct.
Baron et a l . (5)
speculated that factors such as unfavorable environmental
conditions, and treatment of young, weak or diseased plants
would reduce plant tolerance to hexazinone.
Peters et al. (51) reported significant injury and
yield reduction of alfalfa when hexazinone was applied to
nondormant alfalfa in the spring.
Hexazinone applied to
dormant alfalfa at 1.1 kg/ha reduced forage yield 15% (51).
Waddington (71) reported that alfalfa initially injured by
dormant applications of hexazinone at a rate of 1.0 kg/ha
recovered rapidly. He further reported that applications of
hexazinone resulted in increased alfalfa seed yield over a 4
year period.
Chlorsulfuron
Chlorsulfuron (2-chloro-N-[[(4-methoxy-6-methyl-l,3,5triazin-2-yl)amino]carbonyl]benzenesulfonamide) formerly DPX
4189, is a herbicide produced by the E .I . DuPont Co.
It is a member of the sulfonylurea family.
(29).
The
sulfonylureas contain a benzene ring linked to a triazine
ring by a sulfonylurea bridge.
Various side groups attached
to the rings elicit different herbicidal properties
7
(Figure 3) (55).
Chlorsulfuron is formulated as a 75% active ingredient
dry flowable and is marketed under the trade name of "Glean"
(29).
Chlorsulfuron is moderately soluble in acetone and
methylene chloride (29,36), and water solubility is
2.8g/100g H^o at pH 7 (29).
The half life of chlorsulfuron
in an aqueous solution at pH 7 of chlorsulfuron is I month
(29) .
Figure 3.
Molecular structure of chlorsulfuron.
Chlorsulfuron is degraded by soil microbes (34) and by
acid hydrolysis reactions in soil (49).
Microbial
degradation in soil occurs more rapidly when moisture,
temperature, pH, and nitrogen and carbon content are optimal
for microbial growth (34).
Acid
hydrolysis proceeds more
rapidly at high soil temperature, high soil moisture and low
soil pH (49).
Soil texture is not a major factor affecting
8
the rate of degradation (29).
While chlorsulfuron adsorption to clay is low, it has
some affinity for organic matter (29).
The Freundlich K
value for chlorsulfuron on a Flanagan silt loam is 0.69,
comparable to the soil adsorption properties of metribuzin
(29).
Burkhart (10) reported Freundlich K values for
chlorsulfuron ranging from 0.85 to 2.49 using 6 Montana
soils and reported that as soil pH decreases chlorsulfuron
adsorption increases.
Chlorsulfuron phytotoxicity is limited to organisms
that require biosynthesis of valine and isoleucine for
survival (39).
The oral LD^q of chlorsulfuron for rat,
quail, and duck is greater than 5000 mg/kg (29).
These
organisms acquire valine and isoleucine from food sources
which may account for the low chlorsulfuron toxicity.
Chlorsulfuron is a potent inhibitor of cell division in
common soybean (Glycine max L. ) roots (53).
In conjunction
with a reduction in cell division, DNA synthesis was reduced
80%.
Ray (53j proposed that chlorsulfuron indirectly
affected DNA synthesis because there was no effect on DNA
polymerase or thymidimine kinase activity, DNA synthesis in
isolated nuclei, or DNA precursors.
Ray (53) reported that
other cellular functions were not significantly affected by
chlorsulfuron in a 2 hour time frame.
Rqst (60) proposed that chlorsulfuron inhibited
synthesis of cell cycle-specific RN A .
He reported
9
chlorsulfuron inhibited normal cell cycling of proliferating
meristem.
Chlorsulfuron specifically inhibited the
transition of cells in the G 1 and G2 state to the S (DNA
replication) and M (mitosis) state of cycling cells,
respectively.
He proposed that valine and isoleucine were
key components regulating cell cycling.
Rost (61) reported
that the addition of valine and isoleucine to the growth
medium of cycling cells countered the inhibitory effects of
chlorsulfuron.
The link between the inhibition of valine
and isoleucine synthesis and inhibition of cell division has
not been determined (61).
The mode of action of chlorsulfuron is the inhibition
of valine and ispleucine biosynthesis (54).
Acetolactate
synthase (ALS), an enzyme common in the biosynthesis of
these amino acids (6), is the site of action of
chlorsulfuron (54).
Ray (54) reported ALS I50 values for
chlorsulfuron ranged from 18.5 nM for wheat ( Triticum
aestivum L .) to 35.9 nM for johnsongrass (Sorghum halepense
L.).
Ray further reported that addition of valine and
isoleucine to growth media containing chlorsulfuron reversed
the effects of chlorsulfuron on isolated pea roots.
Matsunaka et a l . (39) reported that chlorsulfuron is a
noncompetitive inhibitor of ALS.
Scloss (63) reported that
sulfometuron methyl [methyl 2-[[[[(4,6-dimethyl-2pyrimidinyl)amino]carbonyl]amino]sulfonyl]benzoate], a
sulfonylurea herbicide, is a competitive, reversible
10
inhibitor of A L S .
Imazapyr [2-[4,5-dihydro-4-methyl-4-(1-
methylethyl)-5-oxo-lH-imidazol-2-yl]-3-pyridinecarboxylic
acid with 2-propanamine (1:1) salt], an imidazolinone
herbicide with the same site of action as the sulfonylureas,
is a noncompetitive, reversible inhibitor of ALS (46).
Each
of these herbicides has been shown to have the same mode and
site of action but presumably with different binding sites
'
on ALS (39,46,63).
Chlorsulfuron, sulfometuron methyl, and imazapyr are
categorized as slow, tight-binding inhibitors (46,75).
Williams and Morrison (75) reported that reversible tightbinding inhibitors affect enzymes at concentrations
comparable to the enzyme concentration.
Alternatively,
classical inhibitors such as compounds that compete with the
substrate cause inhibition only at concentrations
considerably greater than enzyme concentration (75).
Chlorsulfuron is not phytotoxic to wheat and barley {Hordeum
vulgare L .) at rates as high as 125 g/ha, while certain
Brassica species are sensitive to rates as low as 5 g/ha
(27).
Sweetzer (68) reported that the biological basis for
resistance of plants to chlorsulfuron is the metabolism of
chlorsulfuron into nonherbicidal forms.
Foley (25) reported
that wheat metabolized 89% of the chlorsulfuron taken up by
roots from nutrient solution within 24 hr of application.
Sweetzer (68) reported that sugar beet (Beta vulgaris L.), a
species very sensitive to chlorsulfuron, metabolized only 3%
11
of the foliar applied chlorsulfuron within 24 hr after
application.
The herbicide safener, I ,8-naphthalic anhydride (NA),
partially protects pprn seedlings from ehlorsulfuron injury.
I ,8-Naphthalic anhydride applied to corn seeds, or applied
as a foliar spray to corn seedlings protected them from
foliar application of chlorsulfuron but not from
ehlorsulfuron taken up from soil (48).
Rubin and Casida (62) reported that preemergent and
early-postemergent applications of R-25788, a corn safener,
protected some corn varieties from
ehlorsulfuron.
They
reported ALS activity was increased 25% following
application of R-25788, and proposed that the increased
activity may account for some of the safening effects of R25788.
Acetolactate Synthase
Acetolactate synthase, ( A LS, EC 4.1.3.18), also called
acetohydroxy acid synthase, is a key enzyme in the
biosynthetic pathway of isoleucine and valine (6,15).
ALS
is found in the mitochondrial matrix (46) and forms an
enzyme complex associated with four other enzymes involved
in isoleucine and valine synthesis (69).
ALS catalyzes two reactions.
ALS synthesizes one
acetolactate molecule from two molecules of pyruvate (6,15).
Three sequential catalyzed reactions produce valine from
12
acetolactate (15).
Leucine is also an end product of
acetolactate which requires six sequential reactions (15).
The second reaction catalyzed by ALS is the production of
one molecule of °<-acetohydroxybutyrate from one molecule of
°<-ketobutyrate and one molecule of pyruvate (6,15).
Alpha-
hydroxybutyrate undergoes three sequential catalyzed
reactions to produce isoleucine (15).
Other enzymes
involved in the synthesis of valine and isoleucine from
acetolactate and
-ketobutyrate are isomeroreductase (EC
I. 1.1.86), dehydrase (EC 4.2.I.9), valine transaminase, and
isoleucine transaminase (15).
Muhitch et a l . (46) suggested that ALS extracted from
gel filtered maize cells is not part of a multienzyme
complex since it failed to synthesize valine from pyruvate.
In comparison, gel filtered ALS extracted from Neurospora
crassa synthesiszed valine from pyruvate.
A multienzyme
complex should produce valine from pyruvate.
However,
Muhitch et a l . (46) reported that a multienzyme complex
including ALS may exist in vivo.
Six isozymes of ALS have been identified.
Three have
been extracted and purified from higher plants: ALS I , ALS
II, and ALS III (1,39,46,54,64).
Depending on the organism,
each isozyme may be present alone or in combination with
other isozymes.
ALS I is coded for by the iivB gene (15,64)
and is composed of two subunits (20).
The larger subunit,
the catalytic subunit, has a molecular weight of 60 kDa and
13
the smaller subunit, the regulator subunit, is 9.5 kDa (20).
ALS II is composed of four subunits (64).
The two larger
subunits have molecular weights of 59.3 kDa and the two
smaller subunits of 9.7 kDa each (64).
subunits are coded for by the iivG
genes (64), respectively.
subunits.
The large and small
(15,64) and the iIvM
ALS III is composed of two
The larger subunit has a molecular weight of 62
kDa and the small subunit is 17.5 kDa (20).
ALS III is
coded for by ilvH and ilvl (15).
Differences in degree of feedback inhibition, binding
affinity for flavin adenine dinucleotide (FAD) and pH
optimum also differentiate the 3 isozymes of A L S .
ALS I has
less affinity for FAD than ALS II or ALS III (64).
While
FAD is normally associated with oxidation/reduction
reactions, it does not serve ALS in this manner but helps
maintain the conformation of the enzyme (63).
ALS I is more
sensitive to L-valine feedback inhibition than ALS III (15).
The pH optimums of ALS I and ALS III are 7.5 and 9.0
respectively (15).
The properties of ALS in concentrated crude extracts or
partially purified form have been described for several
*
organisms (15,35,46,64,69).
Muhitch et a l . (46) first
purified ALS from plant material.
extract to purity due to lability.
It is difficult to
Schloss et a l . (64), who
developed a technique to purify ALS II isolated from
Salmonella typhimurium, reported FAD greatly increased the
14
stability of the bacterial ALS during purification.
Muhitch
et a l . (46) found FAD did not stabilize ALS during
purification.
ALS I could be the predominant isozyme for
this organism which would.account for the low FAD
requirement.
Tanaka (69) reported that ALS extracted from
the fungus Neurospora crassa was stabilized by pyruvate, the
substrate for ALS, during gel filtration.
Muhitch et a l .
(46) further reported that phenyImethylsulfonyI flouride
(PMSF) and dithiothreitol (DDT)
did not increase stability
of ALS purified from lyophylized maize (Zea mays L.) cells.
They felt that additional stabilizing factors would be
needed to render and purify ALS from eukaryotic sources.
LaRossa and Smulki (35) reported that the site of
action of sulfometuron methyl is ALS II and ALS III.
They
found that ALS I is insensitive to sulfometuron methyl and
proposed that ALS I does not bind cx-ketobutyrate
efficiently, and that sulfometuron methyl may compete for
the same binding site.
They suggested that ALS I differs
markedly in structure from ALS II and ALS III.
Matsunaka (39) reported that ALS from hamsters
(Mesocricetus auratus) has a pH optimum of 7.0 to 7.5 and is
insensitive to chlorsulfuron.
This optimum pH range
coincides with the pH optimum of ALS I , a sulfonylurearesistant isozyme.
There is no information elucidating which isozyme(s) is
sensitive to chlorsulfuron or imazapyr. Muhitch et a l . (46)
(
'
.
15
found that Imazapyr can be removed from ALS by gel
filtration with a resumption of catalytic activity.
Imazapyr does not affect ALS irreversibly.
It has not been
determined if chlorsulfuron is a reversible inhibitor of the
enzyme, like sulfometuron methyl (35).
There have been reports of sulfometuron methyl- and
chlorsulfuron-insensitive A L S .
Tobacco (Nicotiana tabacum
L .) mutants resistant to sulfonylurea herbicides have been
isolated from cell culture, and plants regenerated from
selected cells retained,the resistance trait (12).
Resistance is regulated by a single semi-dominant nuclear
gene mutation (12).
ALS extracted from the resistant cell
lines was less sensitive to sulfonylurea herbicides than
wild-type cell lines (11).
Mutants of Salmonella
typhimuvium resistant to sulfometuron methyl have been
isolated and a mutation in the H v G region has been mapped
(35).
This gene codes for ALS II, an isozyme normally
sensitive to sulfometuron methyl.
Mutants of Escherichia
coli resistant to sulfometuron methyl have also been
isolated (77).
Sequence analysis of the mutant iJvG gene
indicated a single nucleotide change resulting from a
substitution of valine for alanine.
Substitution of serine
for proline resulted in resistance of yeast to sulfonylurea
herbicides (21).
Ray (55) has proposed that the isolation
of resistant genes will enable plant scientists to introduce
sulfonylurea resistance to normally sensitive crop plants.
16
Selecting plants for Herbicide Resistance
Selecting plants for herbicide resistance could be a
useful means of identifying or developing germplasm for crop
breeding.
Crop breeding is a long arduous task and plant
selection is only a small but vital portion of the process.
Proper plant selection procedures are necessary to obtain
quality plant germplasm for further development.
Improper
or inadequate selection procedures can result in low quality
germplasm that requires extra screening.
Faulkner (23) suggested several guidelines when
selecting plants for herbicide resistance.
herbicide should be carefully chosen.
First, the
Selection of a toxic
or outdated herbicide should be avoided.
Also, the
herbicide should control a broad spectrum of weeds common to
the crop of interest.
Second, the crop should have a high
degree of inherent genetic diversity. High genetic diversity
increases the size of the genetic pool and any genetic
combinations resulting from that pool.
Third, if possible,
select a crop that shows some tolerance to the herbicide of
choice.
These suggestions increase the chance of success.
There are three basic methods used to select plants for
herbicide resistance (23).
The first approach is to find
alleles for.herbicide tolerance and combine them with
alleles which promote favorable agronomic traits, a process
called crop hybridization.
The second method, mass
i
17
selection, is commonly used where a superior but susceptible
cultivar is chosen and its tolerance is increased by
intravarietal selection.
A third method uses mutagenesis to
increase tolerance in an existing cultivar.
While
hybridization has been used successfully in a number of
plant species and is plausible for all species (23), the
practicality is questionable.
The agronomic fit of the
hybrid may be too low, and the time involved in successfully
developing an acceptable hybrid can be excessive.
Much of the work done with hybridizing plants for
herbicide resistance has been done with the -triazineresistant plants.
Triazine herbicides inhibit the Hill
reaction of the light reaction of photosynthesis (9,45).
Plants of many species have been discovered with triazine
resistance which possess a modified Hill reaction (4)
controlled by a single easily transferred gene (37).
Machado
et a l . (37) reported that triazine-resistance in turnip rape
{Brassica campestris L.), a weedy species, could be
successfully transfered to Polish rape (Brassica campestris
L .) which has agronomic value.
Another crop successfully
hybridized for herbicide resistance is rutabaga (Brassica
napus L.).
Machado et a l . (37) reported the F 1 progeny of
triazine-sensitive rutabaga and triazine-resistant 1Tower
BC1 t rape was triazine-resistant.
They proposed that
transferring triazine resistance to the Brassica oleracea
species such as cabbage, cauliflower, kohlrabi,broccoli,
18
brussels sprouts, and kale could be accomplished.
They
further proposed that triazine resistant Chenopodium album
L . and Solanum nigrum L. might be utilized as candidates for
crossing with sugar beet (Beta vulgaris L.)) and potatoes
(Solanum tubersum L.) respectively.
Intravarietal selection is directly applicable to
cross-fertilized species (23), however, successful
intravarietal selection is based on the assumption that the
desired trait already exists within a population.
Mass
selection is a common method of intravarietal selection.
Machado et al. (37) reported two risks of mass selection.
First, if the amount of heritable variation in the
population is too low, the maximum level of resistance will
plateau below the desired level, and herbicide sensitivity
will persist.
Second, inbreeding in an attempt to increase
resistance may depress the agronomic fit of the resistant
cultivar.
Warwick (72) developed simazine-tolerant rapeseed
germplasm using three cycles of recurrent selection in the •
variety lRigol which exhibited some tolerance. " However, the
tolerance plateaued below an economical level. McLaughlin
(41) reported that increased resin yields in Grindelia
camporum G . could be achieved using mass selection, however
he reported some inbreeding depression after only 2 cycles
of selection. Devine et a l . (16) was perhaps the first to
report that selection for herbicide tolerance could be
19
accomplished using recurrent selection.
They used five
recurrent selection cycles in birdsfoot trefoil (Lotus
corniculatus L .) to obtain 2,4-D ((2,4-dichlorophenoxy)
acetic acid) tolerant: germplasm.
.,
The third method for selecting herbicide resistance in
plants is mutagenesis of cell cultures (23).
The basic
premise underlying mutagenesis is that one cell can give
rise to billions of cells, many of which will possess
genetic variability (31).
Plants regenerated from cells
variant from the cell culture population are then used as a
source of germplasm.
Faulkner (23) reported that
mutagenesis is especially attractive for selection among
self-fertilized species because a single tolerant mutant
cell could act as the foundation of a new cultivar.
There are problems involved with the use of mutagenesis
of cell cultures for selecting plants for herbicide
resistance.
Cell cultures are less differentiated than
plants and many plant systems are inoperative in cell
culture (26).
Cell culture cannot be used to select plants
for tolerance to herbicides whose mode or site of action
involve mature plant systems such as cuticle, thylakoids,
and chlorophyll (26).
Herbicidal action must reside at the
cell level when using mutagenesis of cell culture systems
(31).
Meredith and Carlson (43) reported that herbicide
tolerance in plant cell cultures exists in four forms.
In
20
the first form, tolerance is expressed -by cultured cells but
is lost when cells are grown in the abscehce of the
herbicide.
This form of resistance is a biochemical
adaptation of the cultured cells in the presence of the
herbicide and not a genetic alteration in the cells.
In the
second form, tolerance is retained by the cell culture in
the presence and in the abscence of the herbicide.
Genetic
changes have occurred however the changes are not Stable.
In the third form, tolerance is stable both in culture and
in regenerated plants in the abscence of the herbicide.
While genetic changes have occurred, they are not stable and
cannot be transmitted genetically to the progeny.
In the
fourth form, tolerance is stable and can be transmitted to
the progeny of regenerated plants.
This form of tolerance
shows a true genetic change with a confirmed inheritance
pattern.
>
There have been several reports of isolated plant cells
that express herbicide resistance.
Herbicide resistant
tobacco plants have been regenerated from cell lines with
resistance to amitrole (IH-I,2,4-triazol-3-amine),
glyphosate (N - (phosphonomethyl)glycine), isopropyl Ncarbamate, picloram (4-amino-3,5,6-trichloro-2pyridinecarboxylic acid), and paraquat (1,1'-dimethyl-4,41bipyridinium ion) (31).
In most of these studies, both
sensitive and resistant plants were regenerated from
resistant callus indicating the resistant trait was, on
21
occasion, not expressed during regeneration (31). Other
plant species that have been cultured for resistance to
herbicides include alfalfa, carrot (Daucus carota L.),
t
soybean (Glycine max L.), and white clover ( Trifolium repens
L. ) (19,31,47).
Faulkner (23) proposed that selection and breeding of
plants for herbicide resistance is economical since the cost
of developing a herbicide-resistant crop is far cheaper than
developing a new herbicide.
Hughes (31) proposed that
resistant crops should be developed and released
concurrently with new herbicides for maximum benefit.
Other
advantages of selecting crops for herbicide resistance are
increased weed control with herbicides that normally would
be toxic to the crop, increased flexibility in crop
rotations that normally would be limited by herbicide
carryover, and availability of a greater number and more
economical herbicides to the producer.
Weed Surveys
Weed surveys document the abundance and geographical
distribution of individual plant species.
If done
systematically, weed surveys provide the data needed to
determine the direct economic losses caused by weeds (18).
The impetus behind recent surveys conducted in Canada, the
U .S ., England, and Australia is to document weed shifts
(70).
Weed surveys fall into 3 general classes: historical
22
weed surveys, perception surveys, and scientific weed
surveys.
Historical weed surveys provide information regarding
weed problems of the past.
Perception surveys measure what
a target population perceives to be problem weeds (24).
Perception surveys are relatively easy and inexpensive to
conduct since they can be conducted by mail or personal
interview (24).
Scientific weed surveys provide
quantitative information.
In the mid-1970's. Dew (17)
designed and implemented a weed survey system based on
statistical principles.
Thomas (38,70) modified the Dew
system and used it in the prairie provinces of Canada.
Variations of the Thomas method have been used in North
Dakota, South Dakota, and Minnesota (24).
Thomas (70) stated the goals of the survey program were
to document the numeric abundance and geographic
distribution of individual weed species, and to provide
quantitative data used to estimate losses due to weeds.
The
Thomas method uses a standardized procedure including
randomized selection of fields, a standardized sampling
period, and a standardized method to select survey points
within each field.
Twenty points are sampled in each field
and the number of each weed species within a given area is
tabulated.
Weed frequency, distribution, density, and the
relative abundance of one weed species in comparison to
other weed species can be easily calculated (70).
23
CHAPTER 2
THE PROBABLE CAUSES OF HEXAZINONE INJURY
TO ALFALFA (Meddcago sativa L .) GROWN FOR SEED
Introduction
There is a small but vital certified alfalfa seed
production industry in Montana.
Weeds are a major
production problem and must be controlled because weed seed
contamination of harvested alfalfa seed severely reduces
seed quality.
In addition, competition for water and
nutrients may reduce seed yields as much as 95% the first
year of production (14).
use on alfalfa.
Few herbicides are available for
Hexazinone, the active ingredient of
"Velpar", has been the most effective and commonly used
herbicide by alfalfa seed producers in Montana.
Although
hexazinone was a valuable herbicide, there were several
instances of hexazinone injury to alfalfa from 1982 thru
1984. The DuPont Company elected to withdraw the hexazinone
label for use on alfalfa in Montana, North Dakota, South
Dakota, and Wyoming in 1985.
Although there are reports of
hexazinone injury to crops in the literature (5,33,51,76),
the exact cause of alfalfa injury due to hexazinone is
unknown.
24
The purpose of this study was to determine which
factor(s ) lead to hexazinone injury in alfalfa.
This
information could then be used to amend the herbicide label
to permit safe use of this valuable herbicide in alfalfa in
Montana.
Methods and Materials
Four methods were used to collect information on the
use of hexazinone on alfalfa grown for seed.
First, a weed
survey was conducted in alfalfa seed fields in the summers
of 1985 and 1986.
Second, a questionaire relating to use of
hexazinone was administered to the alfalfa seed producers at
the time of the field survey.
Third, soil from fields where
hexazinone had been applied was analyzed.
was to establish a field experiment.
The fourth phase
A high rate of
hexazinone was applied at two locations in the fall of 1985.
Several alternative herbicides, and three rates of
hexazinone were applied to hexazinone-treated soil in the
fall of 1986.
Thirty-six randomly selected certified alfalfa seed
production fields were surveyed for weeds in 1985
representing approximately 25% of the fields fifteen
counties.
1985
Surveys were conducted from July 30 to August 25,
using a technique similar to a method developed by
Thomas (70).
Twenty points were sampled using an "M"
pattern which uniformily covered each field.
Each weed
25
species was counted in a I m
2
area at each sampling point.
Weed populations were quantified using seven measurements
described by Thomas (70).
A questionaire was administered to farmers for each
field surveyed to obtain background information on
hexazinone use. Information collected included alfalfa
variety, stand age, time and rate of application of
hexazinone, the use of irrigation, and method of herbicide
application.
Soil from eighteen fields where hexazinone had
been applied was collected in December, 1985.
Alfalfa
injury had occurred in six of the 18 fields sampled.
Fifteen to 20 subsamples were collected from each field
using a 2.5 cm diameter soil core sampler.
The soil was
sampled to a depth of 15 cm, mixed, and oven dried at 60 C
for 48 hr.
Soil samples (150-200 g) were sent to soil
testing laboratories at Montana State University, Harris
Laboratories Inc., Lincoln, Nebraska, and the North Dakota
State University Soil Testing Laboratory, Fargo, North
Dakota.
Each laboratory was asked to perform the following
analyses: organic matter content, pH, cation exchange
capacity, calcium and sodium content, and electrical
conductivity.
laboratory.
Soil textures were
analyzed by the MSU
The results for each soil measurement were
averaged from the three laboratories.
A students t-test
using a 59» level of significance was used to compare each
measurement for fields with injury to fields where no injury
26
occurred.
Field experiments were established in the spring of
1986 in Phillips county (southwest of Malta) and in
Yellowstone county (southwest of Laurel) to determine the
effect of successive annual applications of hexazihone to
alfalfa.
Hexazinone was applied to established> dormant
alfalfa grown for seed at a rate of 1.1 kg/ha using a COgpressurized backpack sprayer on March 3 and March 8, 1986 in
Laurel and Malta, respectively (Table I).
Herbicides were applied 8 and 12 months later to soil
previously treated with hexazinone at Laurel and Malta,
respectively (Table 3).
Fluazifop-P butyl ((R)-2-[4-[[5-
(trifluoromethyl)-2-pyridinyl]oxy]phenbxy]propanoic acid),
the only nondormant treatment tested, was applied on June 2
and 3, 1987 at Laurel and Malta, respectively, using a COgpressurized backpack sprayer equipped with 8003 nozzles
operating at 255 kPa which delivered 200.9 L/ha total
solution.
A nonionic surfactant was added
spray volume at 0.25% (v/v).
to the total
Other treatments were applied
to dormant alfalfa on October 29, 1986 arid March 16, 1987 at
Laurel and Malta, respectively.
Herbicides were applied
using a COg-propelled backpack sprayer using 8003 nozzles
operating at 241 kPa in 201 and 215 L/ha at Laurel and Malta
respectively.
A randomized complete'block experimental
design with three replications per treatment was used for
both sites.
27
Each treatment was replicated three times using a
randomized complete block design and 2m x 6m plots.
Plant
heights were measured and percent crop injury was visually
estimated on June 2 and 3, 1987.
Treatment effects on plant
height and injury were analyzed using the HDS method at the
5% level of significance.
Table I. Soil characteristics and hexazinone application
conditions for research plots at Laurel and
Malta, MT (1986).
PARAMETER
Soil
Soil
Soil
Soil
Soil
LAUREL
pH
Organic Matter (%)
ec (mmhos/cm)
CEC (meq/lOOg)
Texture
Date of Application
Volume (L/ha)
Nozzles
Pressure (kPa)
Temperature C
Relative Humidity (%)
Wind Speed
Crop Stage
MALTA
8.2
2.1
0.4
22.4
41% clay
7.9
3.4
0.7
30.2
46% clay
3—5—86
179
8002
255
4.4
85 .
0
Dormant
3-8-86
335
8004
241
4.4
65
0-8 km/h
Dormant
Results and Discussion
The fifteen weeds most frequently occurring weeds in
Montana alfalfa seed production fields are listed in Table
2.
Hexazinone controls ten of these weed species.
Canada
thistle, common dandelion, and foxtail barley are supressed
by hexazinone at rates approaching 1.1 kg/ha.
Hexazinone's
value to Montana alfalfa seed producers is obvious.
28
Nineteen producers identified during the weed survey
had used hexazinone in the past.
Seven producers reported
Table 2. The 15 most frequently occurring weed species in
certified alfalfa seed fields in Montana in 1985 and 1986.
RANK
WEED
RANK
;
I
Downy Brome
(Bromus tectorum L .)
I.
Field Bindweed
(Convolvulus arvensis L .)
2.
Kochia
(Kochia scoparia L .)
10.
Russian Thistle1
(Salsola kali L .)
3.
Wild Oat1
(Avena fatua L. )
11.
4.
Green Foxtail1
{Setaria viridis L. )
5.
Canada Thistle2
(Cirsium arvense L .)
13.
Quackgrass1
(Agropyron irepens L .)
2
Common Dandelion
(Taraxicum officale L .)
I
Prickly Lettuce
(Lactuca serriola L .)
6.
Tansymustard / Flixweed1
(Descurainia pinnata W. )
{Descurainia sdphia L .)
14.
7.
Redroot Pigweed1
15.
(Amaranthus retroflexus L .)
I
Barnyardgrass
{Echinochloa crus-galli L .)
8.
9.
WEED
12.
Foxtail Barley2 ,
(Hordeum jubatum L .)
i
Common Lambsquarters
(Chenopodium album L .)
Weeds effectively controlled by hexazinone.
Weeds suppressed by hexazinone.
alfalfa injury from hexazinone in a total of 8 fields.
Twelve producers reported no hexazinone injury in a total of
13 fields.
The following discussion is based on a total
population of 19 producers.
While this population is too
small to provide conclusiveness, it represents almost all of
29
the seed producers that had used hexazinone.
Several agronomic factors were investigated as possible
causes of hexazinone injury to alfalfa.
First, successive
annual applications, where hexazinone was applied two or
three years in a row, was considered.
Second, application
of hexazinone to nondormant, actively growing alfalfa was
considered.
Third, application of hexazinone to dryland
alfalfa was considered, however, only one dryland field was
treated with hexazinone and no conclusions could be made.
Fourth, operators were rated for their apparent knowledge
concerning herbicide usage.
Last, the possibility of
alfalfa varietal sensitivity was investigated.
There
appears to be no relation between alfalfa variety and
hexazinone injury since several varieties occurred both in
fields with and without injury.
Twelve producers applied hexazinone in consecutive
years, and three reported alfalfa injury.
High rates of
hexazinone were applied in the second year in all three
fields with injury therefore it appears that herbicide
accumulation may be a factor causing alfalfa injury.
Field
testing of this hypothesis proved inconclusive since no
alfalfa injury or reduction in plant height was observed
when hexazinone was applied two years in a row to research
plots at Malta and Laurel (Table 3).
Two producers reported chlorosis of the upper leaves
and stunting of the crop following application of hexazinone
30
to nondormant alfalfa.
The hexazinone label in 1984 stated
that hexazinone should not be applied to actively growing
alfalfa and research results have shown that foliar
Table
3.
Effect of herbicide treatments applied to
established alfalfa in 1987 which had been previously treated
with 1.1 kg/ha hexazinone on March 3 and 8, 1986.
Treatment
Number
Herbicide
Treatment
Rate of
Application
(kg/ha)
I
2
3
4
5
6
7
8
9
10
11
12
13
Check
Diuron
Hexazinone
Hexazinone
Hexazinone
Hexazinone
+ Diuron
Propham
Simazine
Terbacil
Metribuzin
Pronamide
Fluazifop-P--butyl
Check
1.8
0.8
I .I
1.7
I .I
1.8
3.3
1.3
1.0
I .I
1.7
O .3
Alfalfa
Height
Crop
Injury
(cm)
(%)
27.3a
24.8a
26.8a
25.8a
26.5a
25.8a
Oa
Oa
Oa
Oa
Oa
Oa
25.7a
28.3a
25.8a
26.5a
27.8a
26.5a
26.2a
Oa
Oa
Oa
Oa
Oa
Oa
Oa
.
Means in columns followed by the same letter are not
significantly different as determined by the hsd method
at the 5% level.
application of hexazinone to actively growing alfalfa
resulted in 15% to 37% injury (52).
This portion of the
label should receive increased emphasis by the use of bold
lettering if hexazinone is relabelled for use on alfalfa in
Montana.
Farm operators participating in the weed survey were
rated from I to 5 (5 being excellent and I being poor) on
their apparent knowledge of herbicide application to
31
determine if injury could be due to human error. The mean
rating for operators with alfalfa injury was 3.5.
In
comparison, operators without injury had a mean rating of
3.8.
This small difference, and the subjective nature of
the testing indicate human error is not a major factor in
alfalfa injury following application of hexazinone.
The only soil factors that were significantly correlated
with injury were soil texture and organic matter.
The
average organic matter content for fields with injury was
1.8%.
The average organic matter content for fields without
injury was 2.9% (Figure 4).
The label used in 1984 stated
that hexazinone should not be applied to gravelly soils with
less than 1% organic matter.
This portion of the label may
not be conservative enough to use hexazinone safely on
alfalfa in Montana.
In general, soils in fields with injury were more
coarse textured than fields without injury (Figure 5).
The sand content for soil in fields with injury ranged from
12 to 77% with a mean of 47%.
The sand content for soil in
fields without injury ranged from 11 to 55% with a mean of
30%.
The clay content in fields where injury occurred
ranged from 10 to 73% with a mean of 26%, the clay content
for fields without injury ranged from 15 to 52% with a mean
of 33%.
The hexazinone label of 1984 stated that hexazinone
should not be applied to alfalfa if under stress from
32
4
I
CC
LU
IH
3
I
<
5
U
2
Z
X =1.8
' SE = 3
X = 2.9
; SE = .2
<
O
CC
O
1
as '
O
INJURY
NO
INJURY
Figure 4 . Percent organic matter content of soils in fields
with and without hexazinone injury to alfalfa.
1 OOl
INJURY
NO
INJURY
Figure 5. Percent sand and clay content of soils in fields
with and without hexazinone injury to alfalfa.
I
33
weather conditions, or damage from insects or diseases.
This statement is meaningless in Montana since hexazinone is
applied to dormant alfalfa when there is no apparent stress.
The label should restrict hexazinone use to irrigated
alfalfa in Montana in order to avoid use of hexazinone on
alfalfa that may endure stress later in the season.
Hexazinone injury potential appears to increase dramatically
when drought stress occurs.
Also, hexazinone should not be
used on coarse textured soils where irrigation water is
limited.
There are areas of Montana where irrigation water
is rarely available the entire growing season, a condition
which can frequently create severe stress.
Hexazinone was a valuable and popular herbicide for
alfalfa seed producers in Montana.
Adoption of the label
changes suggested above will result in a more conservative
label permitting safer use of hexazinone on alfalfa.
Further research will be necessary to completely understand
the factors which cause hexazinone injury to alfalfa.
34
CHAPTER 3
SELECTING ALFALFA (MedIcago satIva L .)
FOR RESISTANCE TO CHLORSULFURON
Introduction
Alfalfa is a major crop in Montana often grown in
rotation with smq.ll grains.
Although chlorsulfuron is
commonly used for control of broadleaf weeds in small
grains, alfalfa seedlings are very sensitive to direct
applications and to soil residues of this persistant
herbicide.
Chlorsulfuron-resistant alfalfa would allow the
f
use of chlorsulfuron in a cereal grain-alfalfa rotation
system and would provide an effective means of weed control.
Plant breeders have selected for herbicide tolerance in
the past by treating a large number of plants with a
herbicide and selecting survivors (2,16,22).
This
technique, termed mass selection, was suggested by Faulkner
(23) to be considerably less expensive than developing new
( herbicides for use in a particular crop.
Screening of
I
seedlings in the field by mass selection permits the testing
of a large number of plants under high selection intensity
(23).
This technique is most applicable to cross-
fertilizing species which possess high levels of genetic
35
variability and that have been bred less intensively.
Alfalfa is a cross-pollinated autotetraploid therefore it is
.
an excellent candidate for mass selection.
Faulkner (23) suggested that the herbicide used for
developing plant tolerance should be safe, inexpensive, and
provide broad spectrum weed control.
This investigation was
initiated in an attempt to identify and characterize
I•
■
.
■ .'
chlorsulfuron-tolerant alfalfa seedlings.
i
Methods and Materials
Alfalfa seedling selection for chlorsulfuron tolerance.
Chlorsulfuron was applied with a COg-pressurized backpack
sprayer at a rate of 35 g ai/ha to an area 30 by 50 m at the
Post Research Farm, Bozeman, Montana on April 15, 1985.
The
herbicide mixture was applied in 94 L/ha of water at 276
kPa.
Forty-one kg of alfalfa seed from 40 Montana adapted
cultivars was blended and planted I cm deep with a grain
drill on April 19, 1985 at a seeding rate of 273 kg/ha.
Fifteen alfalfa plants survived and were transplanted into
23 cm diam by 23 cm deep pots in chlorsulfuron-free soil
[Bozeman silt loam: peat moss: sand (3:1:1)] on August
15,1985 and placed in the greenhouse.
Chlorsulfuron Tolerance Testing.
Surviving plants were
cloned by stem cuttings and maintained as individual
numbered lines.
The lower node was trimmed of leaf material
and inserted into soil in 2.5 cm diam by 15 cm deep
36
conetainers (Ray Leach Cone-tainers, Canby, OR).
Stem
r
cuttings were also taken from field-grown plants of the
chlorsulfuron sensitive cultivars Ladak 65 and Apollo II to
serve as controls.
Alfalfa plants that were fairly uniform
in size, approximately 10 cm tall, were selected.
Chlorsulfuron was applied to the foliage, and as a soil
drench, at a rate of 35 g/ha 8 weeks after cuttings were
planted.
Foliar applications of chlorsuifuron were made
with a moving belt, fixed nozzle, CO2-pressurized greenhouse
sprayer operating at 242 kPa in 202 L/ha of water containing
0.25% v/v nonionic surfactant (X-77, Chevron Chemical Co.).
The plants were returned to the greenhouse and arranged in a
completely randomized design with 10 replications per
treatment (I plant/replication).
The foliage was trimmed to
a height of 3 cm 14 days after application.
Twenty-one days
after application, regrowth was clipped, dried for 5 days at
60C and weighed.
The experiment was conducted twice using
different plants in the second experiment.
Soil drench applications of chlorsuifuron were applied
at a rate of 35 g/ha.
Two hundred twenty-six ul of a IOuM
solution of chlorsuifuron was pipetted onto the soil surface
in the conetainers followed by 2 ml of water to leach
chlorsuifuron into the soil.
The plants were arranged in a
randomized complete block design with 5 replications per
treatment (I plant/replication).
Each rack of plants was
randomly rotated with other racks of plants in the
37
greenhouse every 2 days to reduce light and temperature
effects. Plant height was recorded at the time of
application and 21 days following herbicide treatment.
After 21 days of treatment, above ground biomass was
clipped, dried and weighed.
Acetolactate Synthase Sensitivity to Chlorsulfuron.
Aceto-
lactate synthase (ALS) was extracted from shoots in each
alfalfa line to determine sensitivity to chlorsulfuron.
Eight to IOg of fresh plant material was homogenized in a
Waring blender in four volumes of chilled extraction buffer
containing 0.1 M K2HPO4 , 1.0 mM pyruvate, 5 mM
dithiothreitol (DTT), IOuM Flavin adenine dinucleotide
(FAD), and 15% v/v glycerol.
The final pH of the buffer was
adjusted to 8.0 using 2.8 M phosphoric acid.
Between 32 to
40 ml of homogenate was filtered through eight layers of
cheesecloth.
Phenylmethylsulfonyl flouride (PMSF),
dissolved in approximately 50 ul of acetone, was added to
the filtrate at I mM.
The mixture was centrifuged at
20,OOOg at 4C for 30 min.
ALS was extracted from the
supernatent with 20 and 60% (w/v) with (NH4 )2SO4 .
The
precipitate was pelleted by centrifugation at 20,OOOg for 60
min at 4C.
ALS was recovered by dissolving the pellet in a
small volume of chilled desalting buffer containing 2OmM
K2HPO4 , IOmM pyruvate and 0.05 mM MgCl2 the desalting buffer was adjusted to 7.5.
The final pH of
ALS was desalted
by gel chromatography in a 12 cm column containing G-25
38
Sephadex.
The desalted ALS was collected in
centrifuge tubes.
chilled 10 ml
ALS was either frozen at -40C or assayed
immediately for ALS activity.
ALS activity was determined using the Westerfield
method (74).
Chlorsulfuron was added to assay buffer
containing 20 mM KgHPO^, 20 mM pyruvate, 0.5mM thiaminepyrophosphate , 0.5 mM MgCl2 and IOuM FAD.
buffer pH was adjusted to 7.0.
The final assay
Chlorsulfuron was added at
the beginning of each assay to obtain a final concentration
of 0, 5, 10, 20, 40, and 80 nM.
One hundred Ul of ALS
extract was added to 400 ul of assay buffer containing
chlorsulfuron.
Following a 30 min incubation at 30 C, 25 ul
of 12N H2SO4 was added, and the assay solution was again
incubated at GOC for 15 min.
Each acidified sample received
500 ul of 2.5% (w/v) creatine and 500 ul of freshly prepared
0.5% (w/v)
<x-naphthol dissolved in 2.5 N NaOH and incubated
for an additional 15 min at 60C.
Absorbance was measured at.
525 nm and the ALS activity was calculated from a standard
curve prepared by measuring absorbance of eleven known
concentrations of acetoin from 0 to 8 ug.
The concentration
of chlorsulfuron needed to reduce ALS activity 50% (I50) was
calculated using a regression equation prepared from several
known concentrations of chlorsulfuron for each ALS extract:
39
In (A) = B q + B 1X
ln (A50) = B0 + B 1X
where:
A = ALS activity
A50 = ALS activity x 0.5 at [chlorsulfuron = 0 ]
X = [chlorsulfuron (nM)]
Results and Discussion
The rate of chlorsulfuron used (35 g/ha) was twice the
label recommendation for wheat and more than 20 times.the
rate required to kill alfalfa seedlings (10).
This intense
selection resulted in 15 healthy alfalfa plants from
approximately 20 million seeds sown. Plants 4 and 10 could
not be cloned due to low vigor and were discarded.
Chlorsulfuron tolerance among the selected lines varied
(Figure 6).
Lines I, 2, 9, and 13 exhibited tolerance
similar to Ladak 65 and Apollo II with both foliar and soilapplied chlorsulfuron.
These lines may have escaped injury
as a result of nonuniform field conditions.
Lines 6,8,11,
and 12 demonstrated tolerance to both foliar and soilapplied chlorsulfuron while lines 14 and 15 were more
tolerant to foliar application than to a soil drench.
Line
3, 5, and 7 were tolerant to soil but not foliar
application.
This variations among lines indicates that
more than one source of tolerance may exist between the
selected plants.
The I50 value of ALS for chlorsulfuron was determined
o
fr
z 150
BOVE GROUND
o
o
u. 125
CL
O
u) 25
<1
O
55 O
I
2
3
5
6 7 8
9
ALFALFA
Il
12
13
14
15
LINE
❖
Bars denoted by an asterisk (*) are significantly different from
the control as determined by the Isd method at the 5% level.
Figure 6. Tolerance of alfalfa plants to 35 g/ha chlorsulfuron
applied as a foliar spray and as a soil drench.
41
for the eight lines which displayed tolerance to the
herbicide (Table 4).
The I50 values of lines 3 and 7 were
4.6 and 2.2 times higher, respectively, than Ladak 65 and
Apollo II.
Lower sensitivity of ALS to chlorsulfuron may
partially account for whole plant tolerance to
chlorsulfuron.
ALS I^q values and ALS response curves to
chlorsulfuron in the remaining lines were similar to both
Ladak 65 and Apollo II (Figure 7).
It is possible that
tolerance to chlorsulfuron in these lines may result from
reduced uptake or translocation, or increased metabolism of
chlorsulfuron.
If tolerance were due to reduced herbicide
uptake or translocation, cell or tissue culture selection
methods would have been inadequate since these tolerance
mechanisms are expressed only at the whole plant level (23).
Herbicide tolerant plants selected from a sensitive
population are usually less agronomically "fit" (52).
Preliminary greenhouse results indicate that the growth
potential of all eight lines is equal to or greater than the
cloned Ladak 65 or Apollo II material (Table 5).
Field
testing is underway to test agronomic fitness.
Mass selection of seedlings for herbicide resistance is
an excellent alternative to cell culture selection in
certain situations.
The success demonstrated here in
identifying chlorsulfuron-resistant alfalfa is most likely a
result of the genetic diversity of alfalfa and chlorsulfuron
sensitivity may be determined by as few as one gene (55).
42
Table 4.
Comparison of acetolactate synthase (ALS) I50
values for Ladak 65 and Apollo II and 8 chlorsulfuron
tolerant alfalfa lines1 .
Alfalfa
Line
(No. )
3
5
6
7
8
11
. 12
14
Ladak 65
Apollo II
Acetolacfate Synthase
(nM of chlorsulfuron)
69c
23a
14a
34b
16a
23a
17a
•18a
16a
14a
Means followed by the same letter are
not significantly different as determined
by the Isd method at the 5% level.
Table 5. Biomass produced by Ladak 65 and Apollo II and
alfalfa lines selected for chlorsulfuron tolerance 21 days
after clipping in the greenhouse1 .
ALFALFA
LINE
3
5
6
7
8
11
12
14
Ladak 65
Apollo II
BIOMASS PRODUCTION
(mg DW/21 day)
99.0b
36.2a
41.5a
41.0a
23.3a
38.3a
47.9a
29. Ia
33.2a
30. Oa
Means followed by the same letter are not
significantly different as determined by
the Isd method at the 5% level.
4
O
o 2
CHLORSULFURON
(nM)
Figure 7. The activity of acetolactate synthase (ALS) from
Ladak 65 alfalfa at 8 concentrations of chlorsulfuron.
44
Tolerance to ch^orsulfuron has been demonstrated in a
population of only 20 million seeds.
This suggests
tolerance among weed species to sulfonylurea herbicides may
also be relatively common and could result in a rapid
expression of weed resistance to this herbicide group under
field conditions.
Techniques similar to this approach may be useful for
other cross-pollinated crops such as corn (Zea mays L.),
sugar beet [Beta vulgaris L.), and sunflower (Helianthus
annuus L.), and other herbicides whose site of action is
coded for by few genes or whose site of action is an enzyme,
including glyphosate [N - (phosphonomethyl)glycine] and
paraquat (1,1'-dimethyl-4-4 1-bipyridinium ion)
(23,32).
Continued investigations include determining agronomic
fitness and seed production under field conditions are .
presently underway.
45
CHAPTER: FOUR
A
WEED
SURVEY OF ALFALFA SEED PRODUCTION
IN MONTANA
FIELDS
Introduction
Montana ranks 8th in the nation in total certified
alfalfa seed production (13) with 11,616, 8,154, and 6,805
acres of certified alfalfa seed acreage in 1984, 1985, and
1986, respectively. (44).
The demand for Montana seed among
northern tier states remains high because seed of many
varieties produced in less harsh climates lacks sufficient
winter hardiness.
Weed control is a vital component of certified alfalfa
seed production.
Although numerous cultural and chemical
control practices exist, weeds continue to be a problem for
the alfalfa seed producer.
A heavy infestation of mixed
weeds can reduce seed yield 95% (14).
A weed survey, based on the method of Thomas (70) was
conducted in 36 and 23 fields in 1985 and 1986,
respectively.. In addition, producers completed a
questionaire for each field to provide background
information on the weed control practices used.
In
addition, a perception survey was conducted in 1985 to
46
identify those weeds producers felt were most troublesome.
The purpose of this study was to identify the weed
species in alfalfa seed fields, to determine which weed
control practices were being used, and to determine the
effectiveness of the various control practices.
Methods and Materials
Thirty-six of a total of 132 certified alfalfa seed
fields listed with the Montana Seed Growers Association, and
23 of 111 certified fields were randomly selected and
surveyed in 1985 and 1986, respectively (Figures 8 and 9).
Approximately 25% of the fields in each county were selected
for the survey.
Permission to survey fields was obtained
from producers.
Fields in 15 counties were surveyed from July 26 to
August 28, 1985.
Surveys were conducted in 11 counties from
July 30 to August 25, 1986 (Figure 8 and 9).
The survey was based on a method developed by Thomas
(70).
Twenty locations per field were selected that
uniformly covered each field using an "M" pattern.
location each weed species was counted in a Im
wire frame.
2
At each
plot using a
Weed species were reported using common names
accepted by the Weed Science Society of America (73).
Unidentified species were collected and indentified with the
help of Dr. John H. Rumely of the Montana State University
herbarium.
M O N T A N A
Figure 8. Counties and locations of alfalfa seed fields
surveyed in 1985.
MONTANA
Figure 9.
Counties and locations of alfalfa seed fields
surveyed in 1986.
49
. Weed populations were quantified using seven
measurements.
Frequency was the number of fields in which a
given species occurred at least once and was expressed as a
percentage of the total number of fields .
Fk =
n
_X_Y i
x 100
where F,
= frequency value for species k
Y. = presence
(I) or absence (0) of species k in
field i
n = number of fields surveyed
Field Uniformity was the number of sampling locations in
which a species occurred and was expressed as a percentage
of the total number of sampling locations for all fields.
Field uniformity measures the distribution of a weed species
in all the fields surveyed.
A high uniformity indicates
that a weed species occurs frequently throughout all the
fields.
n
20
Ul. = X
X
X i ^ X 100
k -- 20ir~
13
J
t
where Ufc = field uniformity value for species k
X . . = prescence (I) or abscence (0) of species
3
quadrant j in field
Occurrence Field Uniformity
in
was the number of sampling
locations in which a species occurred and was expressed as a
percentage of the total number of sampling locations of
those fields where the species occurred.
Occurrence field
uniformity measures the distribution of a weed species
i
50
throughout only those fields where that species occurs.
A
high occurrence field uniformity indicates that a weed
species occurs frequently throughout those fields where
that weed species found.
UA1, =
n
20
Z
X
X. .. X 100
20 (n-a)
where UA, = occurrence field uniformity value for species
k
a = the number of fields in which the species
is absent
Mean Field Density was calculated by totalling each field
density for a species and dividing by the total number of
fields.
Mean field density measures the average density of
a weed species throughout all of the fields surveyed.
\ H
where
=j
density (expressed as number/m ) value of
species in field i
number of plants in quadrant j ( a
quadrant
is 1 .0 in )
to
MFD,
n
5S
i
Mean Occurrence Field Density was calculated by
totalling each field density for a species and dividing by
only those fields where the species occurred.
Mean
occurrence field density measures the average density of a
weed species in only those fields where it occurred.
51
MOFDk =
n
^
D.
n-a
where a = the number fields in which species is absent
The lowest and the highest field density of each weed
species is presented as Density Range.
The Relative Abundance (RA) is a composite value of the
frequency, occurrence, and density for a species.
Relative
abundance has no units and is used to compare the relative
abundance of one given species to another!
For example, a
species with a RA of 36 would be twice as abundant as a
species with an RA of 18.
RA = RFfe + RUfc + RDfe
where RF. = frequency of species k
______________________ - .
__________ X 100
sum of frequencies for all species
RU
k
field uniformity of species k
X 100
sum of uniformities for all species
RD k
mean field density of species k
X 100
sum of MFD for all species
Producers were asked to identify which weed species
they perceived to be most troublesome in 1985.
The
frequency of the weed species reported was calculated.
A questionaire was completed for each field surveyed to
obtain background information on the field and weed control
practices.
Information collected included ownership,
52
alfalfa variety, age of stand, row spacing, clipping and
thinning practices, weed control practice(s ), use of
irrigation, type of insect pollinators used, and soil type
for fields treated with hexazinone.
Results and Discussion
One hundred thirty-two certified alfalfa seed
production fields were listed with the Montana Seed Growers
Association (MSGA) in 1985.
The number of listings
decreased to 111 fields in 1986.
Fifty-six weed species
were found in 36 fields in 1985 (Table 6) with an average of
o
6 species per field and a density of 35 weeds per Im (Table
7).
Thirty-five weed species were identified in 23 fields
in 1986 (Table 8).
The average infestation was 3 weeds/m
o
and each field contained an average of 5 species (Table 9).
Favorable spring moisture conditions in 1986 resulted
in excellent weed control from cultural practices applied in
the spring of 1986 and from herbicides applied in the fall
of. 1985 and spring of 1986.
Below normal precipitation
occurred in the fall of 1984 and spring of 1985 which
resulted in poor weed control.
Weed populations and
densities varied considerably among fields both survey
years.
The heaviest infestations recorded in individual
fields were 183 and 18 weeds/m2 in 1985 and 1986,
respectively.
The lowest infestations in individual fields
Table 6. Frequency, occurrence, density, and relative
abundance of 56 weed species common to alfalfa seed fields
surveyed in 1985.
PLANT
SPECIES
KOCHIA
(Kochia scoparia L.)
WILD OAT
(Avand FdhAd L.)
GREEN FOXTAIL
(Setaria vlrldls L.)
FIELD BINDWEED
(Convolvulus arvensis L.)
CANADA THISTLE
(CircsIm arvense L.)
RUSSIAN THISTLE
(Salsola Iberlca S.tP.)
TANSYMUSTARD
(Descuralnla plnnata L.)
DOWNY BROME
(Broeus tecterm L.)
COMMON DANDELION
(Taraxacm officinale W.)
REDROOT PIGWEED
(Aearanthus retroflexus L.)
PRICKLY LETTUCE
(Lactuca scarIola L.)
BARNYARDGRASS
(Echinochloa crusgalli I.)
FOXTAIL BARLEY
(Hordeue Jubatm L.)
OCCURRENCE
FIELD
FIELD
FREQUENCY UNIFORMITY UNIFORMITY
(t)
(I)
(%)
MEAN
FIELD
DENSITY
(-----
MEAN
OCCURRENCE
FIELD
DENSITY RELATIVE
DENSITY „ RANGE
ABUNDANCE
NUNBER/r— ---- )
58.3
15.8
27.1
5.9
10.0
.1-129.2
36.1
«7.2
9.3
19.7
1.0
2.1
.1- 21.6
14.9
41.7
16.0
41.1
6.2
14.8
.1-162.5
35.0
41.7
12.5
30.0
1.2
2.8
.1- 12.6
16.6
38.9
5.4
13.9
0.4
1.0
.1-4.5
9.6
36.1
11.3
31.2
2.2
6.1
.1-66.3
18.5
33.3
11.1
36.4
1.6
4.8
.1-39.6
16.0
30.6
12.1
39.5
1.6
5.4
.1-35.3
7.2
27.8
5.0
18.0
0.2
0.7
.1-4.6
7.2
27.8
6.5
23.5
0.4
1.4
.1-7.4
8.6
22.2
2.5
11.3
0.1
0.3
.1-0.8
4.6
22.2
8.8
39.4
1.0
4.7
.1-18.0
1.3
22.2
6.7
30.0
2.9
13.2
.1->100.0
16.3
Table 6 c o n t 1d
PLANT
SPECIES
QUACKGRASS
(Agropyron ropens L.)
YELLOW SWEETCLOVER
(Helilotus officinalis L.)
MEADOW SALSIFY
(Tragopogon pratensis L.)
CURLY DOCK
(Aawvt crispus L.)
WITCHGRASS
(Panictm capillare L.)
WILD BUCKWHEAT
(Polygonua convolvulus L.)
PROSTRATE PIGWEED
(Aaaranthus blitoides L.)
COMMON LAMBSQUARTERS
(Chenopodiua albua L.)
VOLUNTEER GRAIN
(Triticua aestivua L.)
SHEPERDSPURSE
(CapseIla bursa-pastorisL.)
COMMON MILKWEED
(Asclepias syriaca L.)
ANNUAL SUNFLOWER
{Helianthus annuus L.)
FALSE FLAX
(.Caaelina aicrocarpa L.)
POVERTY WEED
(Monolepis nuttalliana G.)
MEAN
FIELD
FIELD
FIELD
FIELD
DENSITY RELATIVE
FREQUENCY UNIFORMITY UNIFORMITY DENSITY DENSITY
RANGE
ABUNDANCE
(---- --NUMBER/* ■
------)
(%)
(%)
(%)
19.4
6.1
31.4
0.5
2.4
.1-13.0
7.7
19.4
1.9
10.0
0.0
0.3
.1-1.0
3.9
19.4
1.3
6.4
0.0
0.1
.1-0.2
3.4
13.9
3.5
25.0
2.8
20.3
13.9
2.4
7.0
0.0
0.5
.1-1.0
3.5
13.9
2.8
20.0
0.1
0.7
.1-2.7
3.8
13.9
2.6
19.0
0.2
1.7
.1-7.2
4.0
13.9
2.8
20.0
0.0
0.6
.1-2.2
3.7
11.1
4.4
40.0
0.2
1.4
.8-2.1
4.7
11.1
0.7
6.3
0.0
0.3
.1-0.7
2.0
11.1
0.8
7.5
0.0
0.3
.1-0.7
2.0
11.1
2.2
20.0
0.0
0.8
.1-2.6
3.0
8.3
0.6
6.7
0.0
0.1
.1
1.5
5.6
3.6
65.0
1.0
18.7
.1-MOO.O
10.2-27.2
13.1
6.1
Table 6
PLANT
SPECIES
SMOOTH PIGWEED
(Aaaranthus hybridus L.)
FIELD PEMNYCRESS
(Thlaspi arvense L.)
PROSTRATE KNOTWEED
(Polygonua aviculare L.)
TUMBLE MUSTARD
(Sisyabriua altissiaua L.)
CUTLEAF NIGHTSHADE
(Solanua trlfloruaH.)
BROAOLEAF PLANTAIN
(Plantago aajor L.)
WESTERN WHEATGRASS
(Agropyron pauclflorua L.)
SLENDER WHEATGRASS
(Agropyron trachycauIua I.)
RIDGE-SEEDED SPURGE
(Euphorbia glyptosperaa E.)
SKELETON WEED
(Lygodesaia juncea L.)
TALL BEGGARTICKS
(Oldens vulgata 6.)
SLIMLEAF LAMBSQUARTERS
(Chenopodiua leptophyIlua N.)
COW COCKLE
(Vaccaria pyraaidata M.)
CORN GROMWELL
(LIthosperaun arvense L.)
cont'd
OCCURRENCE
FIELD
FIELD
FREQUENCY UNIFORMITY UNIFORMITY
l%
k)
\
(I)
(I)
(
MEAN
MEAN
OCCURRENCE
FIELD
FIELD
DENSITY RELATIVE
DENSITY DENSITY
RANGE
ABUNDANCE
Z___________
M M O C B / J -- ---J
X
(-- -- UNU
MBER/*2-
5.6
2.4
42.5
0.1
2.0
.1-4.0
2.4
5.6
1.3
22.5
0.0
0.8
.1-1.4
1.6
5.6
0.6
10.0
0.0
0.3
.1-0.5
1.2
5.6
0.6
10.0
0.0
0.1
.1-0.2
1.1
5.6
1.0
17.5
0.0
1.6
.5-2.6
1.6
5.6
1.3
22.5
0.0
1.5
I.0-1.9
1.7
5.6
1.1
20.0
0.0
0.8
.7-0.8
1.5
5.6
1.0
17.5
0.0
0.8
.7-0.8
1.4
5.6
0.4
7.5
0.0
0.2
.1-0.2
1.0
5.6
0.7
12.5
0.0
0.3
.2-0.3
1.2
5.6
0.3
5.0
0.0
0.1
.1
0.9
2.8
0.4
15.0
0.0
0.3
.3
0.6
2.8
0.1
5.0
0.0
0.1
.1
0.4
2.8
0.3
10.0
0.1
2.5
2.5
0.9
Table 6 cont'd
PLANT
SPECIES
OCCURRENCE MEAN
FIELD
FIELD
FIELD
FREQUENCY UNIFORMITY UNIFORMITY DENSITY
I
(t)
(%)
(%)
I...
PRAIRIE WILLOW
2.8
(Sallx hueulls L.)
AMERICAN VETCH
2.8
(Vlcla augustifolia L.)
0RCHARD6RASS
2.8
{Dactylis gloeerata L.)
WATER CRESS
2.8
{Rorippa nasturtiue-aquaticue L.)
SALTGRASS
2.8
{Distichlis spicata L.)
PERENNIAL SOWTHISTLE
2.8
{Sonchus arvensis L.)
PENN. SMARTWEED
2.8
{Polygonua pennsyIvanicua L.)
ANNUAL SOWTHISTLE
2.8
(Sonchus asper I.)
WHITE CLOVER
2.8
(Trifoliua repens L.)
YELLOW FOXTAIL
2.8
{Setaria faberii I.)
VENICE MALLOW
2.8
{Hibiscus trionua L.)
NICROSERIS
2.8
{Microseris nutans G.)
RUSSIAN KNAPWEED
2.8
(Centaurea repens L.)
MEAN
OCCURRENCE
FIELD
DENSITY RELATIVE
DENSITY
RANGE
ABUNDANCE
.-iHUWtfV
llIHCCDZI
mT—
)
0.1
5.0
0.0
0.7
.7
0.5
0.3
10.0
0.0
0.4
.4
0.6
1.5
55.0
0.3
9.8
9.8
2.2
0.4
15.0
0.0
0.2
.2
0.6
0.6
20.0
0.1
5.3
5.3
1.0
0.1
5.0
0.0
0.1
.1
0.4
0.3
10.0
0.0
0.2
.2
0.5
1.0
35.0
0.0
0.7
.7
1.0
0.3
10.0
0.0
0.3
.3
0.5
0.6
20.0
0.0
0.9
.9
0.8
0.4
15.0
0.0
0.1
.1
0.4
0.4
15.0
0.0
0.6
.6
0.7
0.1
5.0
0.0
0.6
.6
0.5
Table 6 cont'd
PLANT
SPECIES
HORSEWEED
(Conyza canadensis L.)
FLUFFWEED
(Fllago arvensis L.)
OCCURRENCE
FIELD
FIELD
FREQUENCY UNIFORMITY UNIFORMITY
(t)
(I)
(I)
NEAN
MEAN
OCCURRENCE
FIELD
FIELD
DENSITY RELATIVE
DENSITY DENSITY
RANGE
ABUNDANCE
(---- -NUMBER/, —
-)
2.8
0.1
5.0
0.0
0.1
.1
0.4
2.8
0.1
5.0
0.0
0.1
.1
0.4
58
Table 7. Weed density, number of species, moisture source,
seeding method, and weed control practices used In 36
alfalfa seed fields surveyed in 1985.
FIELD
I
2
3
4
5
6
T
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
NEEDS PER 20a2
6
22
32
33
39
47
51
66
73
79
88
122
149
154
160
221
224
224
250
258
291
300
353
383
464
504
690
746
867
987
1126
1175
1647
2970
3216
3668
NUMBER OF
NEED SPECIES
3
2
3
9
4
5
5
5
5
4
3
6
2
10
2
6
5
6
14
3
12
4
6
8
12
12
12
14
11
12
13
4
13
14
11
14
IRRIGATION
METHOD OF
SEEDING
WEED
PROGRAM
YES
YES
YES
YES
NO
NO
NO
YES
YES
YES
NO
YES
NO
YES
YES
YES
YES
YES
YES
NO
YES
YES
YES
YES
NO
YES
YES
NO
NO
NO
YES
NO
NO
YES
YES
YES
RONS
ROWS
RONS
BROADCAST
ROWS
ROWS
BROADCAST
ROWS
BROADCAST
ROWS
BROADCAST
ROWS
BROADCAST
ROWS
ROWS
BROADCAST
ROWS
ROWS
ROWS
BROADCAST
BROADCAST
ROWS
ROWS
ROWS
BROADCAST
ROWS
ROWS
ROWS
ROWS
ROWS
ROWS
BROADCAST
BROADCAST
ROWS
ROWS
ROWS
HEXAZINONE + OIURON
HEXAZINONE
HEXAZINOWE + DIURON
HEXAZINONE + DIURON
EPTC + METRIBUZIN
2,4-06 + TRIFLURALIN
CUT FOR HAY
HEXAZINONE
HEXAZINONE
NETRIBUZIN
CULTIVATION ♦ CUT FOR HAY
CULTIVATION
CULTIVATION + CUT FOR HAY
2.4-06 ♦ TERBACIL
NETRIBUZIN
TERBACIL
HEXAZINONE * DIURON
NONE
2,4-08
NETRIBUZIN
NONE
HEXAZINONE + DIURON
HEXAZINONE
HEXAZINONE
NETRIBUZIN
CULTIVATION
CULTIVATION
NETRIBUZIN
NETRIBUZIN
CULTIVATION
NONE
CUT FOR HAY
METRIBUZIN
NONE
NONE
2,4-06
Table 8. Frequency, occurrence, density, and relative
abundance of 35 weed species common to alfalfa seed fields
surveyed in 1986.
PLANT
SPECIES
NILO OAT
(Avena fatua L.)
BARNYARDGRASS
(Echinochloa crusgalli I.)
GREEN FOXTAIL
(Setarla viridls L.)
CANADA THISTLE
(Clrslua arvense L.)
REDROOT PIGWEED
(Amaranthus retroflexus L.)
TAWSYMUSTARD
(Descurain1a pInnata L.)
KOCHIA
(Kochia scoparia L.)
QUACKGRASS
{Agropyron repens L.)
DOWNY BROME
(Bromus tectorue L.)
FOXTAIL BARLEY
(Hordeum jubatum L.)
PRICKLY LETTUCE
(Lactuca scariola L.)
COMMON MILKWEED
{Asclepias syriaca L.)
COMMON LAMBSQUARTERS
(Chenopodium album L.)
MEAN
OCCURRENCE MEAN
OCCURRENCE
FIELD
FIELD
FIELD
FIELD
DENSITY RELATIVE
FREQUENCY UNIFORMITY UNIFORMITY DENSITY DENSITY
RANGE
ABUNDANCE
(---- --NUMBER/,, —
(I)
(%)
(I)
43.5
8.7
20.0
0.5
1.2
.1-8.7
36.3
34.8
4.3
12.5
0.1
0.5
.2-.7
16.0
34.8
7.2
20.6
0.2
0.5
.1-1.7
22.1
30.4
4.1
13.6
0.1
0.4
.1-.9
15.2
26.1
2.4
20.0
0.0
0.2
.1-.2
9.6
26.1
3.0
11.7
0.1
0.2
•1-.5
11.0
26.1
2.4
9.2
0.1
0.3
.1-1.2
10.6
26.1
4.3
16.7
0.4
1.7
.1-4.4
24.7
17.4
3.7
21.3
0.1
0.8
.4-1.3
12.3
13.0
1.5
11.7
0.0
0.3
•1-.4
5.5
13.0
2.4
18.3
0.0
0.3
.2-.5
6.6
13.0
0.9
6.7
0.0
0.2
.2
4.5
13.0
2.2
16.7
0.0
0.3
.2-.4
6.7
Table 8 cont'd
PLANT
SPECIES
COMMON DANDELION
(Taraxacim officinaleW.)
DODDER
(Cuscuta spp. L.)
RUSSIAN THISTLE
{Salsola Iberica S.ftP.)
CUTLEAF NIGHTSHADE
(Solanua triflorim N.)
ORCHARDGRASS
{Dactylis gloaerata L.)
SMOOTH 8ROME
{Broous inerais L.)
YELLOW SWEETCLOVER
{Melilotus officinalis L.)
SMOOTH PIGWEED
{Aaaranthus hybridus L.)
WILD ROSE
{Rosa arkansana P.)
SILVER SAGE
{Arteaisia cana L.)
PEPPERWEED
(Lipidiim perfoliatua L.)
FRINGED SAGEWORT
(Arteaisia frigida L.)
WILD BUCKWHEAT
(Polygonua convolvulus L.)
ANNUAL SUNFLOWER
(HeIianthus annuus L.)
MEAN
OCCURRENCE MEAN
OCCURRENCE
FIELD
FIELD
FIELD
FIELD
DENSITY RELATIVE
FREQUENCY UNIFORMITY UNIFORMITY DENSITY DENSITY
RANGE
ABUNDANCE
— NUMBER/* ■
(X)
(I)
(X)
8.7
1.1
12.5
0.0
0.2
.1-.2
3.5
8.7
0.4
5.0
0.0
0.1
.1
2.4
8.7
2.4
27.5
0.1
1.0
.3-1.8
7.6
4.3
0.2
5.0
0.0
0.1
.1
1.3
4.3
3.9
90.0
0.2
4.5
4.5
11.8
4.3
0.6
15.0
0.0
0.4
.4
2.0
4.3
0.2
5.0
0.0
0.1
.1
1.3
4.3
0.4
10.0
0.0
0.3
.3
1.7
4.3
0.2
5.0
0.0
0.1
.1
1.3
4.3
0.6
15.0
0.0
0.3
.3
2.0
4.3
1.1
25.0
0.0
0.7
.7
3.2
4.3
0.4
10.0
0.0
0.2
.2
1.7
4.3
0.2
5.0
0.0
0.1
.1
1.3
4.3
1.5
35.0
0.0
1.0
1.0
4.0
k
Table 8 cont'd
plaNT
SPECIES
POVERTY WEED
(Honolepis nuttalliana G.)
WESTERN WHEATGRASS
(Agropyron pauciflorua L.)
PUNCTUREVINE
(Tribulus terrestris L.)
SALTGRASS
(Distichlis spicata L.)
YELLOW FOXTAIL
(Setavia lutescens H.)
CURLY DOCK
(Ruaex crispus L.)
MEADOW SALSIFY
(Tragopogon pratensis L.)
OCCURRENCE
FIELD
FIELD
FREQUENCY UNIFORMITY UNIFORMITY
(%)
(*)
(%)
MEAN
FIELD
DENSITY
(-----
MEAN
OCCURRENCE
FIELD
DENSITY RELATIVE
DENSITY , RANGE
ABUNDANCE
NUMBER/,'------ )
4.3
1.7
40.0
0.2
4.5
4.5
9.4
4.3
0.2
5.0
0.0
0.3
.3
1.5
4.3
1.1
25.0
0.0
0.4
.4
2.6
4.3
0.2
5.0
0.0
0.6
.6
2.1
4.3
0.6
15.0
0.0
0.4
.4
2.3
4.3
0.4
10.0
0.0
0.1
.1
1.0
4.3
0.2
5.0
0.0
0.1
.1
1.3
62
Table 9. Weed density, number of species, moisture source,
seeding method, and weed control practices used in 23
alfalfa seed fields surveyed in 1986.
FIELD
I
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
NEEDS PER 20#'
0
2
10
20
23
24
25
26
29
35
37
39
41
44
53
74
75
79
84
121
128
137
354
NUMBER Of
NEED SPECIES
I
2
4
4
7
5
2
4
4
4
6
5
6
5
4
4
9
5
5
3
4
9
9
IRRIGATION
NO
YES
YES
YES
YES
YES
YES
YES
YES
NO
YES
YES
YES
YES
YES
YES
NO
YES
YES
YES
NO
YES
YES
METHOD OF
SEEDING
NEED
PROGRAM
RONS
RONS
RONS
RONS
RONS
BROADCAST
BROADCAST
RONS
RONS
BROADCAST
BROADCAST
RONS
RONS
BROADCAST
RONS
RONS
BROADCAST
RONS
RONS
RONS
BROADCAST
BROADCAST
RONS
NETRIBUZIN
NETRIBUZIN
NETRIBUZIN
TERBACIL
DIURON
METRIBUZIN
HEXAZINONE
DIURON
NETRIBUZIN
NETRIBUZIN
HEXAZINONE
DIURON
NETRIBUZIN
NETRIBUZIN
METRIBUZIN
METRIBUZIN
NONE
NETRIBUZIN
NETRIBUZIN
NETRIBUZIN
NONE
NONE
NONE
63
were 0.3 and 0 weeds/m2 in 1985 and 1986, respectively.
Cultural weed control practices were used as the sole
means of weed control in 70% of the dryland fields surveyed
and on less than 20% of the irrigated fields surveyed.
Early spring cultivation with sweeps perpendicular to
the rows is used by many growers to thin the alfalfa stand
and eliminate weeds.
Row cultivation with sweeps early in
the growing season is also used.
A third practice involved
clipping early in the growing season prior to heading out of
the weeds.
The five most frequently occurring weeds where only
cultural control practices were used were kochia,
tansymustard, downy brome, Russian thistle and Canada
thistle (Table 10).
An average of 7 weed species at a
density of 23.5 weeds/m^ occurred in these fields.
Seven herbicides were used in fields surveyed in 1985
and 1986 (Tables 7 and 9).
The five most frequently
occurring weeds in chemically treated fields were field
bindweed, wild oat, green foxtail, Canada thistle, and
kochia (Table 11).
An average of 6.1 weed species at a
2
density of 12.3 weeds per Im occurred in these fields.
Metribuzin or hexazinone were used in 79% of the chemicallytreated fields.
Metribuzin use increased significantly in
1986 because hexazinone registration was cancelled in
Montana.
Few producers utilized pre-plant herbicides such
as EPTC (S-ethyl dipropyl carbomothioate) or benefin (N-
64
Table 10. The most frequently occurring weed species
Infesting alfalfa.seed fields where cultural control
practices were used.
NUMBER OF FIELDS
1985
KOCHIA
(Kochia scoparia L .)
TANSYMUSTARD
{Descurainia pinnata L. )
DOWNY BROME
{Bromus tectorum L .)
CANADA THISTLE
(Cirsium arvense L.)
RUSSIAN THISTLE
{Salsola iberica S.fiP.)
WILD OAT
(Avena fatua L .)
REDROOT PIGWEED
(Amaranthus retroflexus
FIELD BINDWEED
(Convolvulus arvehsis L .
GREEN FOXTAIL
(Setaria viridis L .)
COMMON MILKWEED
(Asclepias syriaca L. )
1986
TOTAL
7
I
8
6
2
8
5
I
6
5
0
5
4
I
5
4
0
4
3
0
3
I
I
2
2
0
2
. I
0
I
Table 11. The most frequently occurring weed species
infesting alfalfa seed fields where chemical control
practices were used.
NUMBER OF FIELDS
FIELD BINDWEED
(Convolvulus arvensis L .)
WILD OAT
(Avena fa tua L .)
GREEN FOXTAIL
(Setaria viridis L.)
CANADA THISTLE
(Cirsium arvense L.)
KOCHIA
(Kochia scoparia L.)
BARNYARDGRASS
(Echinochloa crusgalli L .)
REDROOT PIGWEED
(Amaranthus retroflexus L. )
QUACKGRASS
(Agropyron repens L .)
COMMON DANDELION
( Taraxacum officinale W . )
TANSYMUSTARD
(Bescurainia pinnata L.)
1985
1986
TOTAL
13
12
25
14
10
24
12
8
20
12
7
19
14
5
19
8
8
16
10
6
16
7
6
13
10
2
12
3
3
6
66
butyl-N-ethyl-2,6-dinitro-4-(trifluoromethyl)benzenamine)
because of cost, inconsist e n c y a n d the inability to seed a
companion crop.
application.
Many fields were treated by custom aerial
Ground applications were normally applied by
the producers.
Weed densities for three newly seeded fields densities
ranged from 1.1 to 183 weeds/m^.
Two of the fields had been
treated with 2,4-DB (4-(dichlorophenoxy)butyric acid) in
spring after seeding.
Trifluralin (2,6-dinitro-N,N-
diprropyl-4-(trifluoromethyl)benzenamine) was applied pre­
plant incorporated to the third field which was relatively
weed-free.
Twenty-three weed species were identified in the
3 surveyed fields (Table 12).
Fields treated with 2,4-DB
contained 13 and 14 weed species compared to 5 weed species
for the trifluralin-treated field (Table 7).
Annual grassy
weeds dominated first year stands.
Twenty-four of 36 fields surveyed in 1985, and 19 of 23
fields surveyed in 1986, were irrigated (Tables 7 and 9).
Nearly all of the alfalfa seed production fields in the Milk
river and the upper Yellowstone river areas are irrigated.
Irrigated fields had slightly more weed species (52) than
dryland fields (46) (Table 13 and 14);
Field bindweed, the
most common weed under irrigation, was found in 74% of the
fields surveyed while green foxtail occurred at the highest
density (16.4 plants/m2 ) (Table 14).
The average irrigated
2
field contained 6.5 weed species at 19.1 weeds/m . Dryland
Table 12. Frequency,
occurrence,
density,
and relatitve
abundance of weed species common to new seedings of alfalfa
surveyed in 1985.
pLAnt
SPECIES
KOCHIA
{Kochia scoparia L.)
GREEN FOXTAIL
{Setiria viridis L.)
VOLUNTEER GRAIN
[Triticua aestivua L.)
WILD OAT
{Aveni fatua L.)
PROSTRATE KNOTWEED
(,Polygonua aviculare L.)
BARNYARDGRASS
(Echinochloa crusgalH L.)
MEADOW SALSIFY
(Tragopogon pratensis L.)
FIELD BINDWEED
(Convolvulus arvensis L.)
PRICKLY LETTUCE
(Lactuca scariola L.)
CANADA THISTLE
(Clrsiua arvense L.)
WITCHGRASS
(Panicua caplllare L.)
FALSE FLAX
(CaaeIIna aIcrocarpa A.)
OCCURRENCE
FIELD
FIELD
FREQUENCY UNIFORMITY UNIFORMITY
(I)
(I)
(I)
MEAN
MEAN
OCCURRENCE
FIELD
FIELD
DENSITY RELATIVE
DENSITY DENSITY
RANGE
ABUNDANCE
(---- --NUMBER/*2-
100.0
16.7
16.7
1.2
1.2
.1-2.4
18.0
66.7
40.0
60.0
54.5
81.8
.1-163
105.0
66.7
35.0
52.5
1.3
1.9
1.7-2.I
22.4
66.7
30.0
<5.0
5.0
7.5
1.0-13.9
26.0
33.3
1.7
5.0
0.0
0.1
.1
3.8
33.3
8.3
25.0
0.2
0.6
.6
6.7
33.3
1.7
5.0
0.0
0.1
.1
3.8
33.3
8.3
25.0
0.3
0.8
.8
6.9
33.3
5.0
15.0
0.1
0.4
.4
5.3
33.3
1.7
5.0
0.2
0.6
.6
4.1
33.3
5.0
15.0
0.3
1.0
1.0
5.6
33.3
1.7
5.0
0.0
0.1
.1
3.8
Table 12 cont'd
PLANT
SPECIES
COMMON DANDELION
(Taraxacua officinale N.)
COMMON NILKHEED
(Asclepias syriaca L.)
RUSSIAN THISTLE
(Salsola iberica S.iP.)
SKELETON WEED
(Lygodesaia juncea L.)
SMOOTH PIGWEED
(Aaaranthus hybridus L.)
TANSYNUSTARD
(Descurainia pinnate L.)
FIELD PENNYCRESS
(Thlaspi arvense L.)
REOROOT PIGWEED
(Aaaranthus retroflexus L.)
COMMON LAMBSQUARTERS
{Chenopodiua albua L.)
RIDGE-SEEDED SPURGE
(Euphorbia glyptosperaa E.)
YELLOW SWEETCLOVER
(Helilotus officinalis L.)
DOWNY BROME
(Broaus tectorua L.)
FOXTAIL BARLEY
(Hordeua jubatua L.)
OCCURRENCE
FIELD
FIELD
FREQUENCY UNIFORMITY UNIFORMITY
lk\
lk\
lk\
(t)
(
%)
(I)
MEAN
MEAN
OCCURRENCE
FIELD
FIELD
DENSITY RELATIVE
DENSITY DENSITY , RANGE
ABUNDANCE
Z_______
(--- ---uimceB/-2
NUMBER/*2----- )»
33.3
6.7
20.0
0.1
0.3
.3
6.0
33.3
1.7
5.0
0.0
0.1
.1
3.8
33.3
10.0
30.0
0.1
0.4
.4
7.2
33.3
3.3
10.0
0.0
0.1
.1
4.4
33.3
1.7
5.0
0.0
0.1
.1
3.8
33.3
30.0
90.0
1.7
5.2
5.2
17.8
33.3
1.7
5.0
0.0
0.1
.1
3.8
33.3
16.7
50.0
0.7
2.1
2.1
10.9
33.3
5.0
15.0
0.1
0.2
.2
5.3
33.3
3.3
10.0
0.1
0.2
.2
4.6
33.3
1.7
5.0
0.0
0.1
.1
3.8
33.3
1.7
5.0
0.0
0.1
.1
3.8
33.3
6.7
20.0
0.1
0.3
.3
6.0
Table 12 cont'd
PLANT
SPECIES
PROSTRATE PIGWEED
(AMaranthus blitoides L.)
TALL BEGGARTICKS
{Bldens vulgata I.)
OCCURRENCE
FIELD
FIELD
FREQUENCY UNIFORMITY UNIFORMITY
(I)
(I)
(!)
MEAN
MEAN
OCCURRENCE
FIELD
FIELD
DENSITY RELATIVE
DENSITY DENSITY
RANGE
ABUNDANCE
(---- — NUMBER/e2— ---- )
33.3
1.7
5.0
0.0
0.1
.1
3.8
33.3
1.7
5.0
0.0
0.1
.1
3.8
Ol
IO
Table 13.
Frequency, occurrence, density, and relative
abundance of weed species common to dryland alfalfa seed
fields surveyed in 1985 and 1986.
MEAN
OCCURRENCE MEAN
OCCURRENCE
PLANT
FIELD
FIELD
FIELD
FIELD
DENSITY RELATIVE
SPECIES
FREQUENCY UNIFORMITY UNIFORMITY DENSITY DENSITY , RANGE
ABUNDANCE
(X)
(X)
(X)
(--- -- NUMBER/* — ---- )
DOWNY 8R0ME
{Braaus tectorua L.)
TANSYNUSTARD
(DescuraInia pInnata L.)
RUSSIAN THISTLE
(Salsola iberica S.&P.)
FIELD BINDWEED
(Convolvulus arvensls L.)
KOCHIA
(Kochia scoparia L.)
MEADOW SALSIFY
(Tragopogon pratansis L.)
PRICKLY LETTUCE
(Lactuca scariola L.)
CANADA THISTLE
(Cirsiua arvense L.)
FOXTAIL BARLEY
(Hordeua jubatua L.)
WILD BUCKWHEAT
(Polygonua convolvulus L.)
COMMON LAMBSQUARTERS
(Chenopodiua albua L.)
TUMBLE MUSTARD
(Sisyabriua altissiua L.)
SHEPERDSPURSE
(CapseIla bursa-paston's i.)
93.8
41.6
55.5
6.4
8.5
.4-35.3
39.1
81.3
29.4
47.0
5.5
8.8
.1-39.6
31.4
62.5
29.6
52.6
8.0
14.2
.1-66.3
35.8
50.0
5.8
18.6
0.4
1.4
I.0-1.7
7.3
50.0
23.1
52.8
20.6
47.1
.1-129
57.1
37.5
4.8
15.4
0.1
0.2
.1-.2
6.1
31.3
3.8
12.2
0.1
0.2
.1-.3
5.6
25.0
5.8
30.9
0.2
1.2
.6-1.1
5.2
25.0
4.8
25.6
0.3
1.2
.2-2.7
5.0
25.0
10.5
42.0
0.4
1.4
.1-2.7
7.9
18.8
8.3
44.3
0.3
1.4
.1-2.2
6.1
18.8
3.0
16.0
0.8
4.0
.1-9.0
5.1
18.8
2.3
12.3
0.1
0.6
.1-.7
3.5
Table 13 cont'd
PLANT
SPECIES
CUTLEAF NIGHTSHADE
(Solanua trifloruaH.)
WILD OAT
(Avena fatua L.)
GREEN FOXTAIL
{Setaria vlridis L.)
YELLOW SWEETCLOVER
(Melilotus officinalis L.)
ORCHARDGRASS
(Dactylis gloaerata L.)
REDROOT PIGWEED
(Aaaranthus retroflexus L.)
WITCHGRASS
(Panicua capillare L.)
ANNUAL SUNFLOWER
(HelIanthus annuus L.)
VOLUNTEER GRAIN
(Triticua aestiwa L.)
SKELETON WEED
(Lyqodesaia juncea L.)
SMOOTH PIGWEED
(Amaranthus hybridus L.)
FIELD PENNYCRESS
(Thlaspi arvense L.)
PROSTRATE KNOTWEEO
(Polygonua aviculare L.)
COW COCKLE
(Vaccaria pyraaidata M.)
OCCURRENCE
FIELD
FIELD
FREQUENCY UNIFORMITY UNIFORMITY
/t
I)
N
ik)
(
(I)
MEAN
MEAN
OCCURRENCE
FIELD
FIELD
DENSITY RELATIVE
DENSITY DENSITY
RANGE ' ABUNDANCE
x
Z
Uv
IR
lw
it
MK
C/
BH
/J
t
- W
\_____
-J
18.8
3.0
24.0
0.1
0.4
.4
3.0
18.8
3.0
16.0
0.2
1.0
.5-1.0
3.9
18.8
15.8
84.3
1.9
10.1
1.1-12.0
12.3
18.8
3.8
20.3
0.1
0.7
.1-1.0
4.2
12.5
10.4
83.2
1.1
8.6
4.5-9.8
7.9
12.5
6.0
48.0
0.8
6.6
.3-7.4
5.6
12.5
3.0
24.0
0.1
0.4
.4
2.8
12.5
0.8
6.4
0.0
0.2
.1-.2
1.9
12.5
8.3
66.4
0.3
2.2
I.0-2.7
5.3
12.5
3.0
24.0
0.1
0.4
.2-.6
2.8
12.5
0.8
6.4
0.0
0.2
.1-.3
2.2
6.3
4.5
72.0
0.2
2.4
2.4
2.0
6.3
1.5
3.0
0.1
2.5
2.5
0.7
6.3
0.8
12.8
0.0
0.1
.1
0.3
Table 13 cont'd
PLANT
SPECIES
SALTGRASS
(Distich7is spicata L.)
TALL BEGGARTICKS
(Bidens vulgata G.)
ANNUAL SONTHISTLE
(Sonchus asper L.)
BROAOLEAF PLANTAIN
(Plantago aajor L.)
COMMON DANDELION
(Taraxacue officinale N.)
CORN GROMWELL
(Lithospereue arvense L.)
PENN. SMARTWEED
(Polygonue pennsyIvanicue L.)
POVERTY WEED
(Honolepis nuttalliana G.)
WESTERN NHEATGRASS
(Agropyron pauciflorue L.)
PERENNIAL SOWTHISTLE
(Sonchis arvensis L.)
CURLY DOCK
{Rueex crispus L.)
SLIMLEAF LAMBSQUARTERS
(Chenopodiue leptophyHue L.)
PROSTRATE PIGWEED
(Aearanthus blitoides L.)
FALSE FLAX
(CaeeIina eicrocarpa A.)
OCCURRENCE
FIELD
FIELD
FREQUENCY UNIFORMITY UNIFORMITY
(%)
(*)
(*)
MEAN
MEAN
OCCURRENCE
FIELD
FIELD
DENSITY RELATIVE
DENSITY DENSITY
RANGE
ABUNDANCE
/ _ ._
_
_
M
lI
H
O
C
D
/
«
—
H
U
f
lo
t
K
/
*
I
- )
6.3
3.0
48.0
0.6
3.0
9.0
2.0
6.3
0.8
12.8
0.1
1.0
1.0
0.4
6.3
3.8
60.8
0.1
1.1
1.1
1.2
6.3
4.5
72.0
0.2
3.2
3.2
2.1
6.3
0.8
12.8
0.1
1.0
1.0
0.4
6.3
0.8
12.8
0.3
4.3
4.3
0.9
6.3
0.8
12.8
0.0
0.3
.3
0.3
6.3
0.8
12.8
0.0
0.2
.2
0.3
6.3
2.3
36.8
0.0
0.2
.2
0.9
6.3
0.8
12.8
0.0
0.2
.2
0.3
6.3
0.8
12.8
0.0
0.2
.2
0.3
6.3
1.5
24.0
0.0
0.5
.5
0.6
6.3
0.8
12.8
0.0
0.2
.2
0.3
6.3
0.8
12.8
0.0
0.2
.2
0.3
Table 13 c o n t 1d
PLANT
SPECIES
FRINGED SAGEWORT
{Artaiisli friglds L.)
DODDER
(Cusati spp. L.)
WILD ROSE
(Rosa Arkansana P.)
SILVER SAGE
(Arteaisia cana L.)
PEPPERWEED
(Lepidiua perfolIatua L.)
OCCURRENCE
FIELD
FIELD
FREQUENCY UNIFORMITY UNIFORMITY
(I)
(I)
(I)
MEAN
FIELD
DENSITY
(--- —
MEAN
OCCURRENCE
FIELD
DENSITY RELATIVE
DENSITY ? RANGE
ABUNDANCE
NUMBER/*------ )
6.3
0.6
9.6
0.0
0.5
.5
0.2
6.3
0.3
4.8
0.0
0.7
.7
0.1
6.3
0.3
4.8
0.0
0.2
.2
0.1
6.3
0.6
9.6
0.1
0.8
.8
0.2
6.3
1.3
20.8
0.1
1.6
1.6
0.3
-j
w
Table 14. Frequency, occurrence, density, and relative
abundance of weed species common to irrigated alfalfa seed
fields surveyed in 1985 and 1986.
PLANT
SPECIES
FIELD BINDWEED
(Convolvulus arvensis L.)
WILD OAT
(Avena fatua L.)
GREEN FOXTAIL
(Setaria viridis L.)
CANADA THISTLE
(Clrsiue arvense L.)
KOCHIA
(Kochia scoparia L.)
BARNYAROGRASS
(Echlnochloa crusgalli L.)
RE0R00T PIGWEED
(Aearanthus retroflexus L.)
QUACKGRASS
(Agropyron repens L.)
COMMON DANDELION
(Taraxactm officinale L.)
FOXTAIL BARLEY
(Hordeue Jubatue L.)
TANSYMUSTARD
(Descurainia pinnata L.)
PRICKLY LETTUCE
(Lactuca scariola L.)
COMMON MILKWEED
(Asclepias syriaca I.)
OCCURRENCE
FIELD
FIELD
FREQUENCY UNIFORMITY UNIFORMITY
(X)
(I)
(I)
MEAN
MEAN
OCCURRENCE
FIELD
FIELD
DENSITY RELATIVE
DENSITY DENSITY
RANGE
ABUNDANCE
I■"HUratK/*
\
)
58.1
18.6
32.0
1.3
2.3
.1-12.6
31.2
55.8
12.0
21.5
1.6
2.8
.1-21.6
26.6
46.5
13.3
28.5
4.9
10.5
.1-162.5
44.7
<4.2
5.5
12.4
0.3
0.8
.1-4.5
13.1
44.2
9.5
21.3
0.5
1.0
.1-6.1
16.7
37.2
9.7
26.3
0.9
2.5
.1-9.7
18.4
32.6
5.6
17.1
0.2
0.5
.1-2.1
10.3
30.2
8.0
26.2
0.8
2.8
.1-13.0
15.5
25.6
4.7
18.2
0.2
0.6
.1-4.6
8.5
20.9
5.3
25.6
2.4
11.4
16.3
4.2
25.7
0.2
1.0
.1-5.2
6.7
16.3
2.8
17.1
0.1
0.3
.1-.8
5.0
16.3
1.2
7.1
0.0
0.2
.1-.7
3.7
.1-MOO.O
20.7
Table 14 cont'd
PLANT
SPECIES
RUSSIAN THISTLE
(Salsola Iberica S.&P.)
YELLOW SWEETCLOVER
(Helilotus officinalis L.)
CURLY DOCK
(Rueex crispus L.)
SLIMLEAF LAMBSQUARTERS
(Chenopodiim leptophyHue N.)
WITCHGRASS
{Panicue capillare L.)
MEADOW SALSIFY
(Tragopogon pratensis L.)
PROSTRATE PIGWEED
{Aearanthus blitoides L.)
POVERTY WEED
(Honolepis nuttalliana G.)
WESTERN WHEATGRASS
(Agropyron pauciflorue L.)
ANNUAL SUNFLOWER
{Helianthus annuus L.)
VOLUNTEER GRAIN
(Triticue aestivue L.)
SALTGRASS
{Dlstichlis spicata L.)
RIDGE-SEEDED SPURGE
{Euphorbia glyptosperea E.)
FALSE FLAX
{CaeelIna eicrocarpa A.
OCCURRENCE MEAN
FIELD
FIELD
FIELD
FREQUENCY UNIFORMITY UNIFORMITY DENSITY
(--- —
(I)
(%)
(I)
14.0
3.9
27.5
0.2
14.0
1.1
7.5
0.3
14.0
3.1
22.5
11.6
1.6
9.3
MEAN
OCCURRENCE
FIELD
DENSITY RELATIVE
DENSITY ? RANGE
ABUNDANCE
NUMBER/* ------ -)
1.1
.1-4.4
6.0
0.2
.1-.6
3.2
2.4
16.9
.1-MOO.O
14.0
0.0
0.2
.1-.4
3.2
1.6
17.5
0.1
0.5
.1-1.0
3.0
9.3
0.4
5.0
0.0
0.1
.1
1.8
9.3
2.1
22.5
0.2
2.0
.1-7.2
4.1
7.0
4.0
56.7
1.0
14.2
4.5-27.2
9.7
7.0
1.1
22.5
0.0
0.6
.3-.8
2.2
7.0
2.5
35.0
0.2
3.0
.1-7.6
4.2
4.7
1.8
40.0
0.1
1.5
.8-2.1
2.5
4.7
0.6
12.5
0.1
3.0
.6-5.3
2.0
4.7
0.3
7.5
0.0
0.1
.1-.2
1.0
4.7
0.2
5.0
0.0
0.1
.1
0.9
17.8
Table 14 c o n t 1d
PLANT
SPECIES
SLENDER WHEATGRASS
(Agropyron trachycoulua L.)
SHEPERDSPURSE
(Capse17a bursa-pastoris L.)
CUTLEAF nightshade
(Solanua triflonm N.)
WILD BUCKWHEAT
(Polygonua convolvulus L.)
DOWNY BROME
(Broaus tectorua L.)
YELLOW FOXTAIL
(Setaria glauca L.)
PROSTRATE KNOTWEED
(Polygonua aviculare L.)
WHITE CLOVER
(Trifoliua repens L.)
HORSEWEED
(Conyza canadensis L.)
FLUFFWEED
(FIIago arvensis L.)
RUSSIAN KNAPWEED
(Centaurea repens L.)
FIELD PENNYCRESS
(Thlaspi arvense L.)
TALL BEGGARTICKS
(Bidens vulgata G.)
VENICE MALLOW
(Hibiscus trionua L.)
OCCURRENCE MEAN
FIELD
FIELD
FIELD
FREQUENCY UNIFORMITY UNIFORMITY DENSITY
(----—
(t)
(t)
(X)
MEAN
OCCURRENCE
FIELD
DENSITY RELATIVE
DENSITY „ RANGE
ABUNDANCE
NUMBER/*'
4.7
0.8
17.5
0.0
0.8
.7-.8
1.5
4.7
0.2
5.0
0.0
0.1
.i
0.9
4.7
0.3
5.0
0.1
1.4
.1-2.6
1.3
4.7
0.2
5.0
0.0
0.1
.1
0.9
4.7
0.2
5.0
0.0
0.1
.1-.5
0.9
4.7
0.8
17.5
0.0
0.7
.4-.9
1.5
2.3
0.1
5.0
0.0
0.1
.1
0.4
2.3
0.2
10.0
0.0
0.3
.3
0.5
2.3
0.1
5.0
0.0
0.1
.1
0.5
2.3
0.1
5.0
0.0
0.1
.1
0.5
2.3
0.1
5.0
0.0
0.6
.6
0.6
2.3
0.1
5.0
0.0
0.1
.1
0.5
2.3
0.1
5.0
0.0
0.1
.1
0.5
2.3
0.1
5.0
0.0
0.1
.1
0.5
»i
Ol
Table 14 cont'd
PLANT
SPECIES
OCCURRENCE MEAN
FIELD
FIELD
FIELD
FREQUENCY UNIFORMITY UNIFORMITY DENSITY
/
(t)
(%)
(I)
I
MICROSERIS
2.3
(MieraserIs nutans G.)
8R0ADLEAF PLANTAIN
2.3
(Plantago aajor L.)
SMOOTH PIGWEED
2.3
(Aearanthus hybridus L.)
WATER CRESS
2.3
(Rorippa nasturtium-aquaticua L.)
AMERICAN VETCH
2.3
(Vlcia austifolia L.)
PRAIRIE WILLOW
2.3
(Salix huailis L.)
SMOOTH BROME
2.3
(Bromus inermis I.)
DODDER
2.3
[Cascuta spp. L.)
PUWCTUREVINE
2.3
{Tribulus terrestris L.)
MEAN
OCCURRENCE
FIELD
DENSITY RELATIVE
DENSITY
RANGE
ABUNDANCE
'"RUMOCK/# -
0.3
15.0
0.0
0.6
.6
0.7
0.1
5.0
0.0
1.0
1.0
0.6
1.8
80.0
0.1
4.0
4.0
2.2
0.3
15.0
0.0
0.2
.2
0.6
0.2
10.0
0.0
0.4
.4
0.6
0.1
5.0
0.0
0.7
.7
0.6
0.4
15.0
0.0
0.4
.4
0.7
0.1
5.0
0.0
0.1
.1
0.5
0.6
25.0
0.0
0.4
4
0.9
78
fields contained 5.8 weed species at 21.1 weeds/m2 .
Downy
brome, the most frequently occurring dryland species,
occurred in 76.5% of the fields surveyed (Table 13) and
kpchia occurred at the highest density at 20.6 plants/m2
(Table 13).
Seventy-one percent of the fields were seeded in rows
and the rest were broadcast seeded.
from 51 to 160 cm.
Row spacings ranged
Row-seeded alfalfa was weedier than
broadcast-seeded fields.
Broadcast-seeded fields contained
o
an average of 6.2 species at 13;04 weeds/m . Row-seeded
alfalfa contained an average of 6.7 species at 22.7
2
weeds/m . Chemical control was used in ten of the 16
broadcast-seeded fields and 34 of the 43 row-seeded fields
surveyed.
Row cultivation was the most common method of cultural
control used in row-seeded alfalfa and clipping was the most
common cultural method of control in broadcast-seeded
fields.
A strong preference was indicated among producers
for row-seeded alfalfa.
Lack of proper seeding equipment
was the main reason for not seeding alfalfa in rows among
those producers who broadcast seed.
There are 3 areas where alfalfa seed is produced in
Montana, the Milk river drainage of northern Montana, the
upper Yellowstone river drainage, and the lower Yellowstone
drainage of southern Montana (Figure 10).
While there are
pockets of seed production in other locations in the state,
M O N T A N A
MILK RIVER
UPPER
YELLOWSTONE
LOWER
YE LL OWS TO NE
Figure 10. Counties of the Milk river, lower Yellowstone river, and upper
Yellowstone river alfalfa seed production regions of Montana.
80
the majority of producers are found in those three areas.
The upper Yellowstone river region covers parts of
Yellowstone, Carbon, Big Horn, and Treasure counties.
Sixty-nine percent of the fields surveyed in this region
were irrigated.
Seed production is mainly confined to the
Yellowstone and the Big Horn river basins^
Thirty-seven
weed species were identified in 13 fields (Table 15).
The
five most frequently occurring weeds were (in order): Canada
thistle, field bindweed, kochia, wild oat, and prickly
lettuce.
Few of the producers relied on cultural control
practices for weed control.
The Milk river region covers parts of Blaine and
Phillips counties.
All of the fields surveyed in this
region were irrigated and were located on the Milk river
bottomland on very heavy soils (Bowdoin soil series)
unsuitable for annual cropping systems.
Thirty-four weed
species were identified in 16 fields surveyed (Table 16).
The five most frequently occurring weeds were (in order):
wild oat, field bindweed, quackgrass, green foxtail, and
kochia.
Chemical weed control techniques were used on all
of the fields surveyed in this region.
Foxtail barley had
the highest population density of the 34 weed species
identified and it occurred in 31% of the fields surveyed
with an average of 6.4 plants/m2 (Table 16).
The lower Yellowstone river region covers parts of
Rosebud, Custer, and Powder River counties.
Most of the
Table 15. Frequency,
occurrence, density,
and relative
abundance of weed species common to alfalfa seed fields
surveyed in the upper Yellowstone river alfalfa seed
production region.
PLANT
SPECIES
CANADA THISTLE
(Clrsiuu arvense L.)
KOCHIA
(Kochia scoparia L.)
FIELD BINDWEED
{Convolvulus arvensis L.)
WILD OAT
{Avena fatua L.)
COMMON MILKWEED
{Asclepias syriaca L.)
FOXTAIL BARLEY
(Hordeuu jubatuu L.)
REDR00T PIGWEED
{Auaranthus retroflexus L.)
PRICKLY LETTUCE
{Lactuca scariola L.)
YELLOW SWEETCLOVER
(Helilotus officinalis L.)
TANSYMUSTARD
(Decurainia pinnata L.)
COMMON DANDELION
(Taraxacuu officinale W.)
WITCHGRASS
(Panicuu cap11Iare L.)
OCCURRENCE
FIELD
FIELD
FREQUENCY UNIFORMITY UNIFORMITY
W
(I)
(t)
MEAN
FIELD
DENSITY
f
MEAN
OCCURRENCE
FIELD
DENSITY RELATIVE
DENSITY
RANGE
ABUNDANCE
_il||HfiPD/■
.. )
\
56.3
10.0
14.4
0.5
0.7
53.8
11.2
20.7
10.2
18.9
50.0
15.8
25.6
0.5
25.0
8.1
26.3
25.0
1.5
25.0
.1-1.1
22.0
.1-129.2
32.5
0.8
.1-2.4
26.7
0.9
3.8
.1-13.9
15.1
5.0
0.1
0.2
.1-.2
7.9
4.2
13.8
0.3
0.8
.1-2.7
10.5
25.0
4.2
13.8
0.2
0.6
.1-1.9
10.5
25.0
5.0
16.3
0.1
0.4
.1-.8
11.2
18.8
1.9
8.3
0.1
0.3
.1-.6
7.0
18.8
4.6
20.0
0.1
0.5
.1-.9
9.7
18.8
8.8
38.3
0.4
0.3
.1-4.6
14.2
18.8
4.6
20.0
0.2
0.4
.3-1.0
9.7
Table 15 cont'd
OCCURRENCE
FIELD
FIELD
FREQUENCY UNIFORMITY UNIFORMITY
(I)
(*)
(%)
PLANT
SPECIES
BARNYARDGRASS
(EchInochI crusgaIli I.)
COMMON LAMBSQUARTERS
(Chenopodiua aIbua L.)
QUACKGRASS
(Agropyron repens L.)
GREEN FOXTAIL
(Setarid viridis L.)
ORCHARDGRASS
{Dactylis gloaerata L.)
RUSSIAN THISTLE
(Salsola iberica S.tP.)
SHEPERDSPURSE
(Capsella bursa-pastoris I.)
DOWNY BROME
(Broaus tectorua L.)
MEADOW SALSIFY
(Tragopogon pratensis L.)
DODDER
(Cascuta spp. L.)
HORSEWEED
(Conyza canadensis L.)
FLUFFWEED
(EUago arvensis L.)
WHITE CLOVER
(TrifoLiua repens L.)
VOLUNTEER GRAIN
(Triticua aestivua L.)
MEAN
MEAN
OCCURRENCE
FIELD
FIELD
DENSITY RELATIVE
DENSITY DENSITY
RANGE
ABUNDANCE
(---- -NUMBER/#2-
12.5
2.3
15.0
0.1
0.4
.2-.6
6.3
12.5
1.9
12.5
0.1
0.4
.3-.4
5.8
12.5
7.7
50.0
0.8
5.2
.1-9.3
12.4
12.5
8.5
55.0
12.5
81.4
.4-162.5
24.9
12.5
11.2
72.5
1.1
7.1
4.5-9.8
16.2
12.5
0.8
5.0
0.0
0.2
.1-.4
4.7
12.5
0.8
5.0
0.0
0.2
.1-.3
4.7
12.5
1.9
12.5
0.2
1.0
1.0
5.9
12.5
0.8
5.0
0.0
0.1
.1
4.7
6.3
0.4
5.0
0.0
0.1
.1
2.9
6.3
0.4
5.0
0.0
0.1
.1
2.9
6.3
0.4
5.0
0.0
0.1
.1
2.9
6.3
0.8
10.0
0.0
0.3
.3
3.6
6.3
4.2
55.0
0.2
2.1
2.1
7.2
m
Table 15 cont'd
PLANT
SPECIES
PROSTRATE KNOTWEEO
{ Polygonua aviculare L
.)
FALSE FLAX
(Caaelina aicrocarpa A.)
POVERTY WEED
[Honolepis nuttaliana 6.
SALTGRASS
(Dlstlchlis spicata L.)
WESTERN WHEATGRASS
(Agropyron pauciflorua L.)
PERENNIAL SOWTHISTLE
(Sonchus arvensis L.)
CURLY DOCK
(Puaex crispus L.)
ANNUAL SOWTHISTLE
(Sonchus asper L.)
BROAOLEAF PLANTAIN
{Plantago major L.)
CORN GROMWELL
(LIthosperaua arvense L.)
PENNSYLVANIA SMARTWEED
{Polygonua pennsyIvanicua L.)
MEAN
OCCURRENCE MEAN
OCCURRENCE
F
I
E
L
D
F
I
E
L
D
FIELD
FIELD
DENSITY RELATIVE
FREQUENCY UNIFORMITY UNIFORMITY DENSITY DENSITY
RANGE
ABUNDANCE
Z
n
U
H
O
C
K
/
f
f
l
K*)
V
6.3
0.4
5.0
0.0
0.1
.1
2.9
6.3
0.4
5.0
0.0
0.1
.1
2.9
6.3
6.2
83.0
2.1
27.2
27.2
11.7
6.3
1.5
20.0
0.4
5.3
5.3
4.7
6.3
1.5
20.0
0.1
0.8
.8
4.4
6.3
0.4
5.0
0.0
0.1
.1
2.9
6.3
0.4
5.0
0.0
0.1
.1
3.2
6.3
2.7
35.0
0.1
0.7
.7
5.6
6.3
3.1
40.0
0.2
1.9
1.9
6.1
6.3
0.8
10.0
0.2
2.5
2.5
3.8
6.3
0.8
10.0
0.0
0.2
.2
3.6
Table 16. Frequency, occurrence, density, and relative
abundance of weed species common to alfalfa seed fields
surveyed in the Milk river alfalfa seed production region.
PLANT
SPECIES
WILD OAT
{Avena fatua L.)
FIELD BINDWEED
{Convolvulus arvensis L.)
GREEN FOXTAIL
{Setaria viridis L.)
QUACKGRASS
{Agropyron repens L.)
COMMON DANDELION
{Taraxacm officinale W.)
FOXTAIL BARLEY
{Hordern jubatue L.)
CANADA THISTLE
{Cirsiue arvense L.)
BARNYAROGRASS
{Echinochloa crusgalli L.)
CURLY DOCK
(AUeex crispus L.)
COMMON LAMBSQUARTERS
(Chenopodiue aIbue L.)
PRICKLY LETTUCE
{Lactuca scariola I.)
YELLOW SWEETCLOVER
{HeliIotus officinales L.)
OCCURRENCE
FIELD
FIELD
FREQUENCY UNIFORMITY UNIFORMITY
(t)
(%)
(I)
MEAN
MEAN
OCCURRENCE
FIELD
FIELD
DENSITY RELATIVE
DENSITY DENSITY
RANGE
ABUNDANCE
---)
-NUMBER/*2
—
(----
62.5
16.6
26.5
2.3
3.7
.3-21.6
20.0
50.0
20.6
41.2
2.4
4.8
.8-12.6
30.1
50.0
6.9
13.8
0.3
0.6
.1-1.65
13.0
50.0
12.5
25.0
1.4
2.8
.1-13.0
20.9
37.5
4.7
12.5
0.1
.3
31.0
13.1
42.0
6.4
20.5
31.0
1.8
14.0
0.1
0.4
.1-.5
31.0
9.7
31.0
1.5
4.9
.1-18.0
16.9
31.0
8.1
26.0
6.3
20.3
.1->100
35.8
25.0
3.5
13.8
0.1
0.2
.1-.3
6.0
25.0
3.8
15.0
0.1
0.2
.1-.5
6.2
18.8
1.3
6.7
0.0
0.1
.1-.3
3.7
•1-.6
-3->100
8.9
39.2
6.2
Table 16 c o n t 1d
PLANT
SPECIES
OCCURRENCE MEAN
FIELD
FIELD
FIELD
FREQUENCY UNIFORMITY UNIFORMITY DENSITY
(t)
(t)
(%)
18.8
TANSYMUSTARD
{Descurainia pinnata L.)
12.5
REDROOT PIGWEED
{AMaranthus retroflexus L.)
12.5
BARNYARDGRASS
(Echinochloa crusgalli I.)
ANNUAL SUNFLOWER
12.5
{Helianthus annuus L.)
COMMON MILKWEED
12.5
{Asclepias syriaca L.)
POVERTY WEED
12.5
{Honolepis nuttaliiana G.)
12.5
WESTERN WHEATGRASS
[Agropyron paucifloruM L.)
DOWNY BROME
12.5
(Bromus tectorum L.)
RIDGE-SEEDED SPURGE
12.5
(Euphorbia glyptosperma E.)
SMOOTH BROME
6.3
(Bromus inermis L.)
SMOOTH PIGWEED
6.3
(Amaranthus hybridus L.)
6.3
WATER CRESS
(Rorippa naturtium-aquaticum L.)
SLENDER WHEATGRASS
6.3
(Agropyron trachycaulum L.)
MEADOW SALSIFY
6.3
(Tragopogon pratensis I.)
MEAN
OCCURRENCE
FIELD
DENSITY RELATIVE
DENSITY
RANGE
ABUNDANCE
--NUMBER/*2—
6.9
36.7
0.4
1.9
.1-5.2
8.5
4.1
32.5
0.1
1.2
.2-2.1
5.0
5.0
40.0
0.1
0.4
.3-.6
5.2
6.3
50.0
0.6
4.8
I.0-7.6
8.2
1.3
10.0
0.0
0.1
.1-.2
2.7
5.6
45.0
0.9
7.4
4.5-10.2
9.1
4.4
35.0
0.1
0.5
.3-.7
4.8
0.6
5.0
0.0
0.3
.1-.50
2.3
0.9
7.5
0.0
0.1
.1-.2
2.5
0.9
15.0
0.0
0.4
.4
1.6
6.2
80.0
0.3
4.0
4.0
8.9
0.9
15.0
0.0
0.2
0.2
1.5
1.9
30.0
0.0
0.7
0.7
2.3
0.3
5.0
0.0
0.1
0.1
1.2
Table 16 cont'd
PLANT
SPECIES
VENICE HALLOW
(Hibiscus trionua L.)
NICROSERIS
(Hlcroseris nutans G.)
8ROADLEAF PLANTAIN
(Plantago aajor L.)
YELLOW FOXTAIL
(SetarIa glauca L.)
FIELD PENNYCRESS
(Thlaspi arvense L.)
PROSTRATE PIGWEED
(Polygontm aviculare L.)
TALL BEGGARTICKS
(Bidens vulgata G.)
OCCURRENCE
FIELD
FIELD
FREQUENCY UNIFORMITY UNIFORMITY
(t)
(I)
(I)
MEAN
FIELD
DENSITY
(--- —
MEAN
OCCURRENCE
FIELD
DENSITY RELATIVE
DENSITY ^ RANGE
ABUNDANCE
NUMBER/* ------ )
6.3
0.3
5.0
0.0
0.1
0.1
1.2
6.3
0.3
15.0
0.0
0.6
0.6
1.3
6.3
0.3
5.0
0.1
1.0
1.0
1.4
6.3
1.3
20.0
0.1
0.9
0.9
2.0
6.3
0.3
5.0
0.0
0.1
0.1
1.1
6.3
0.3
5.0
0.0
0.1
0.1
1.1
6.3
0.3
5.0
0.0
0.1
0.1
1.2
87
seed production occurs in the Yellowstone and Tongue river
basins.
A second cluster of producers is located south of
Miles City in the Little Pumpkin creek drainage.
The five
most frequently occurring weeds in the 17 fields surveyed
were (in order): green foxtail, field bindweed, downy brome,
kochia, and barnyardgrass (Table 17).
Russian thistle had
the highest population density of the 31 weed species
identified occurring in 29 % of the fields with a mean
density of 4.2 plants/m2 (Table 17).
Fifty-three percent of
the fields surveyed in this region were nonirrigated.
Russian thistle, redroot pigweed, kochia, Canada thistle,
and tansymustard were the five most common weeds in fields
surveyed outside of the three main seed producing regions
(Table 18).
Fields were located in Gallatin, Petroleum,
Dawson, Broadwater, Choteau, McCone, and Roosevelt counties.
Thirty-seven weed species (more than any other region) were
identified in the 13 fields surveyed (Table 18).
The five most successful weed control practices in 1985
(Table 19) in order were:
1# hexazinbne + diuron applied in the fall,
2# hexazinone applied in the spring,
3# EPTC PPI + metribuzin applied in the fall,
4# trifluralin PPI + 2,4-DB applied postemergence,
5# cutting alfalfa for hay early in the season.
Table 17.
F r e q u e n c y , o c c u r r e n c e , density, and relative
abundance of weed species common to alfalfa seed fields
surveyed in the lower Yellowstone river alfalfa seed
production region.
PLANT
SPECIES
FIELD BINDWEED
{Convolvulus arvensis L.)
GREEN FOXTAIL
{SetarIa viridis L.)
DOWNY 8R0ME
{Bromis tectorua L.)
KOCHIA
{Kochia scoperia L.)
TANSYMUSTARD
{Descurainia pinnate L.)
8ARNYAR06RASS
{Echinochloa crusgalli L.)
RUSSIAN THISTLE
{Salsola iberica S.fcP.)
REDROOT PIGWEED
{Aaaranthus retroflexus L.)
WILD OAT
{Avene fatua L.)
MEADOW SALSIFY
{Tragopogon pratensis L.)
WILD BUCKWHEAT
{Polygonua convolvulus L.)
PRICKLY LETTUCE
{Lactuca scariola L.)
MEAN
OCCURRENCE MEAN
OCCURRENCE
FIELD
FIELD
FIELD
FIELD
DENSITY RELATIVE
FREQUENCY UNIFORMITY UNIFORMITY DENSITY DENSITY
RANGE
ABUNDANCE
_Ul
D/
»
t
R UIMQ
NO P
L K/B
(I)
(I)
(I)
\
59.0
16.2
27.5
0.7
1.2
.1-4.1
6.8
59.0
17.6
30.0
1.6
2.6
.1-12.0
18.8
53.0
21.2
40.0
3.4
6.5
.9-35.3
21.7
47.0
11.5
24.4
3.9
8.3
.1-56.0
13.7
<1.0
9.7
23.6
0.7
1.6
.1-6.2
11.2
41.0
11.1
27.0
0.8
2.0
.1-2.7
12.3
29.0
11.8
40.0
4.2
14.2
.1-66.3
13.8
23.5
4.7
20.0
0.5
2.2
.2-7.4
6.0
23.5
2.1
8.8
0.1
0.4
.1-.6
3.7
18.0
1.2
6.7
0.0
0.1
.1-.2
2.5
18.0
5.3
30.0
0.2
1.1
.3-2.7
5.8
18.0
1.2
6.7
0.0
0.1
.1-.2
2.5
Table 17 cont'd
MEAN
PLANT
SPECIES
CANADA THISTLE
{Cirsiua arvense L.)
WITCHGRASS
[Panicua capillare L.)
TUMBLE MUSTARD
(Sisyabriim altissiaua L.)
ANNUAL SUNFLOWER
(Helianthus annuus L.)
QUACKGRASS
{Agropyron ropens L.)
SALTGRASS
(Distichlis spicata L.)
YELLOW FOXTAIL
[Setaria glauca L.)
COMMON DANDELION
(Taraxacua officinale W.
YELLOW SWEETCLOVER
{Melilotus officinalis L.)
TALL BEGGARSTICK
{Bidens vulgata G.)
PUNCTUREVINE
(TribuIus terrestris L.)
SKELETON WEED
{Lygodesaia juncea L.)
COMMON LAMBSQUARTERS
(Chenopodiua albua L.)
AMERICAN VETCH
(Vicia augustifolia L.)
OCCURRENCE
FIELD
FIELD
FREQUENCY UNIFORMITY UNIFORMITY
(t)
(%)
(%)
MEAN
OCCURRENCE
DENSITY RELATIVE
FIELD
FIELD
RANGE
ABUNDANCE
DENSITY DENSITY
(---- --NUMBER/*2- ---- )
12.0
0.9
7.5
0.1
1.1
.3-1.9
1.9
12.0
1.5
12.5
0.0
0.2
.1-.3
2.2
12.0
0.9
7.5
0.0
0.2
.1-.2
1.8
12.0
0.6
5.0
0.0
0.2
.1-.2
1.5
6.0
0.3
5.0
0.1
2.2
2.2
1.1
6.0
0.3
5.0
0.0
0.6
.6
0.9
6.0
0.9
15.0
0.0
0.4
.4
0.7
6.0
0.3
5.0
0.0
0.1
.1
0.8
6.0
1.5
25.0
0.1
0.1
1.0
1.7
6.0
0.3
5.0
0.0
0.1
.1
0.8
6.0
1.5
25.0
0.0
0.4
4
1.7
6.0
0.3
15.0
0.0
0.3
.3
0.8
6.0
0.3
5.0
0.0
0.1
.1
0.8
6.0
5.6
10.0
0.0
0.4
4
4.7
Table 17 cont'd
PLANT
SPECIES
VOLUNTEER GRAIN
(Trltlcua aestivua L.)
CUTLEAF NIGHTSHADE
(Solanua trlflorua N.)
SLIMLEAF LAMBSQUARTERS
(Chenopodiua leptophyllua I.)
PROSTRATE PIGWEED
(Aaeranthus blitoides L.)
FALSE FLAX
(Caaelin* aicrocarpa A.)
OCCURRENCE
FIELD
FIELD
FREQUENCY UNIFORMITY UNIFORMITY
(t)
(%)
(t)
MEAN
MEAN
OCCURRENCE
FIELD FIELD
DENSITY RELATIVE
DENSITY DENSITY
RANGE
ABUNDANCE
(----- NUMBER/m------ )
6.0
1.8
30.0
0.1
1.0
1.0
2.1
6.0
1.5
2.5
0.5
0.0
.5
1.7
6.0
0.9
15.0
0.0
0.3
.3
1.3
6.0
0.3
5.0
0.0
0.1
.1
0.8
6.0
0.3
5.0
0.0
0.1
.1
0.8
to
O
Table 18.
F r e q u e n c y , o c c u r r e n c e , density,
and relative
abundance of weed species common to alfalfa seed fields
surveyed located in regions other than the Milk river, lower
and upper Yellowstone river alfalfa seed production regions.
PLANT
SPECIES
WILD OAT
(Avens fatud L.)
RUSSIAN THISTLE
{Salsola iberica S.fcP.)
REDR00T PIGWEED
(ABaranthus retroflexus L.)
CANADA THISTLE
(ClrsiuB arvense L.)
KOCHIA
(Kochia scoparia L.)
TANSYNUSTARD
(DescuraInia pinnata L.)
WILD BUCKWHEAT
(Polygonue convolvulus L.)
PROSTRATE PIGWEED
(ABaranthus blitoides L.)
GREEN FOXTAIL
(Setaria viridis L.)
VOLUNTEER GRAIN
(JriticuB aestivuB L.)
MEADOW SALSIFY
(Tragopogon pratensis L.)
OCCURRENCE
FIELD
FIELD
FREQUENCY UNIFORNITY UNIFORNITY
(I)
(I)
(I)
NEAN
NEAN
OCCURRENCE
FIELD
FIELD
DENSITY RELATIVE
DENSITY DENSITY
RANGE
ABUNDANCE
(---- --NUMBER/* —
69.0
13.4
19.4
1.1
1.5
.1-7.9
31.2
61.5
19.6
31.9
0.8
1.3
.1-4.4
34.0
46.2
6.9
15.0
0.2
0.5
.1-1.1
14.5
38.5
5.8
15.0
0.5
1.2
.1-4.5
14.8
38.5
11.5
30.0
0.6
1.6
.1-6.1
20.7
30.8
10.4
33.8
3.1
10.1
.1-39.6
43.9
23.0
1.2
5.0
0.0
0.1
.1
23.0
6.5
28.3
0.6
2.7
.2-7.2
14.6
23.0
21.3
92.5
1.5
6.7
.1-18.7
34.8
15.4
5.8
37.5
0.2
1.3
.8-1.7
8.6
15.4
0.8
5.0
0.0
0.1
.1
3.2
4.7
Table 18 c e n t 1d
MEAN
PLANT
SPECIES
FIELD BINDWEED
(Convolvulus arvensis L.)
COMMON DANDELION
(Taraxacua officinale W.)
SMOOTH PIGWEED
(Aearanthus hybrldus L.)
DOWNY BROME
(Broeus tectorue L.)
FOXTAIL BARLEY
(Hordeue jubatue L.)
QUACKGRASS
(Agropyron repens L.)
SHEPERDSPURSE
(CapseIla bursa-pastoris L.)
CUTLEAF nightshade
(Solanue trlflorueH.)
FALSE FLAX
(Caeelina eicrocarpa A.)
COMMON MILKWEED
(Asclepias syriaca L.)
SKELETON WEED
(Lygodeseia Juncea L.)
FIELD PENNYCRESS
(Thlaspi arvense L.)
COMMON LAMBSQUARTERS
(Chenopodiue aIbue L.)
YELLOW SWEETCLOVER
(Helilotus officinalis L.)
OCCURRENCE
FIELD
FIELD
FREQUENCY UNIFORMITY UNIFORMITY
(%)
(%)
(%)
MEAN
OCCURRENCE
FIELD
FIELD
DENSITY RELATIVE
DENSITY DENSITY
RANGE
ABUNDANCE
(---- -NUMBER/* -
15.4
1.5
10.0
0.0
0.2
.1-.4
3.8
15.4
0.8
5.0
0.0
0.1
.1
3.2
15.4
1.2
7.5
0.0
0.2
.1-.3
3.6
15.4
6.2
40.0
0.1
0.8
.4-.9
8.1
15.4
0.8
5.0
0.0
0.1
.1
3.2
15.4
1.2
7.5
0.0
0.3
.2 .4
3.7
15.4
1.2
7.5
0.1
0.4
.1-.7
3.9
15.4
1.2
7.5
0.2
1.3
.1-2.6
5.3
7.7
0.4
5.0
0.0
0.1
.1
1.6
7.7
0.8
10.0
0.1
0.7
.7
2.3
7.7
0.8
10.0
0.0
0.2
.2
2.0
7.7
3.1
40.0
0.1
1.4
1.4
4.6
7.7
5.0
65.0
0.2
2.2
2.2
6.6
7.7
0.4
5.0
0.0
0.1
.1
1.6
Table 18 cont'd
MEAN
PLANT
SPECIES
WILD ROSE
(Rosa arkansana P.)
SILVER SAGE
(Arteaisia cana L.)
DODDER
(Cuscuta spp. L.)
TUMBLE MUSTARD
(Slsyabriua altissiaua L.)
COW COCKLE
(Vaccaria pyraaidata M.)
RUSSIAN KNAPWEED
(Centaurea repens L.)
SLENDER WHEATGRASS
(Agropyron pauciflorua L.)
PRAIRIE WILLOW
(Salix huaWs L.)
ANNUAL SUNFLOWER
(Helianthus annuus L.)
PEPPERWEED
(Lepidiua perfoliatua L.)
FRINGED SAGEWORT
(Arteaisia frigida L.)
PROSTRATE KNOTWEED
(Polygonua aviculare L.)
OCCURRENCE
FIELD
FIELD
FREQUENCY UNIFORMITY UNIFORMITY
i*\
W
(I)
MEAN
FIELD
DENSITY
Z ...._
I
OCCURRENCE
FIELD
DENSITY RELATIVE
DENSITY
RANGE
ABUNDANCE
HUmJwn/6
7.7
0.4
5.0
0.0
0.1
.1
1.5
7.7
1.2
15.0
0.0
0.3
.3
2.3
7.7
0.4
5.0
0.0
0.1
.1
1.5
7.7
1.2
15.0
0.1
0.9
.9
2.8
7.7
0.4
5.0
0.0
0.1
.1
1.6
7.7
0.4
5.0
0.1
0.6
.8
2.1
7.7
0.4
5.0
0.1
0.8
.1
1.6
7.7
0.4
5.0
0.0
0.1
.1
1.6
7.7
0.4
5.0
0.0
0.1
.1
1.6
7.7
1.9
25.0
0.1
0.7
.7
3.1
7.7
0.8
10.0
0.0
0.2
.2
2.0
7.7
1.2
15.0
0.0
0.5
.5
1.7
94
The 5 most successful weed control practices in 1986
(Table 20) in order were:
1# trifluralin PPI + metribuzin fall applied,
2# metribuzin applied in the spring,
3# metribuzin applied
in the fall,
4# hexazinone applied in the
spring,
5# terbacil applied in the spring.
Nine weed species were perceived by producers as most
troublesome.
These are (in order) Canada thistle, kochia,
quackgrass, green foxtail, Russian thistle, yellow
sweetclover, wild oat, common milkweed, and field bindweed
(Figure 11).
All of these weeds except common milkweed,
field bindweed, and Canada thistle can be controlled with
currently registered herbicides.
Several producers reported they had no "troublesome"
weeds.
They felt their control practices were working
adequately, or the "most troublesome" weed did not effect
seed yield.
It is worth noting that all of the "most
troublesome" species listed are quite visible in a field
with the exception of field bindweed.
Short-statured weeds
which were less visible were frequently not perceived as
being troublesome even though they were often found in very
high densities.
Yellow sweetclover was identified by only
two producers as troublesome however many producers maintain
that yellow sweetclover is easily controlled by rouging.
95
Table 19. Ten most effective weed control practices of
alfalfa seed fields surveyed in 1985.
RATING WEEDS PER 20i2
I.
2.
3.
4.
5.
6.
7.
8.
9.
10.
6
2
32
39
47
51
88
33
149
66
NUMBER Of WEEDS/ZOn2
SPECIES
X NO. SPECIES
3
2
3
4
5
5
3
9
2
5
18
44
96
156
235
255
264
297
298
330
NEED
PROGRAM
HEXAZINONE + DIURON
HEXAZINONE
HEXAZINONE ♦ DIURON
EPTC + NETRIBUZIN
2,4-06 + TRIFLURALIN
CUT FOR HAY
CULTIVATION ♦ CUT FOR HAY
HEXAZINONE ♦ DIURON
CULTIVATION + CUT FOR HAY
HEXAZINONE
Table 20. Ten most effective weed control practices of
alfalfa seed fields surveyed in 1986.
RATING WEEDS PER 20«2
I.
2.
3.
4.
5.
6.
7.
8.
9.
10.
0
2
10
25
20
26
29
24
35
23
NUMBER OF WEEDS/20*2
X NO. SPECIES
SPECIES
I
2
4
2
4
4
4
5
4
7
0
4
40
50
80
104
116
120
140
161
WEED
PROGRAM
NETRIBUZIN
NETRIBUZIN
NETRIBUZIN
HEXAZINONE
TERBACIL
DIURON
METRIBUZIN
NETRIBUZIN
NETRIBUZIN
DIUROW
Figure 11. Most troublesome weeds of alfalfa seed fields as perceived
by the producers.
97
BIBLIOGRAPHY
98
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I
101
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APPENDICES
106
APPENDIX A
1985 Alfalfa herbicide demonstration plots located in
Laurel, Malta, and Miles City
107
HERBICIDE DEMONSTRATION PLOTS
Herbicide demonstration plots were established at
three locations in Montana.
The objective was to show which
herbicides were currently available and labelled for use on
seed alfalfa, and the efficacy of these compounds.
Demonstrations tours were held on July 15, 1986 at the Gary
Knudsen farm located 3 miles west of Malta, MT; July 16,
1986 at the Gary Wiltse river farm located 18 miles south of
Miles City, MT; and on July 17, 1986 at the John Wold farm
located 4 miles west of Laurel, MT.
Background information pertaining to spraying
conditions, soil characteristics and stage of growth of
the weeds at the time of rating are shown in Tables 22, 24,
and 26.
Weed control and alfalfa injury ratings are shown
in Tables 23, 25, 27.
Several people with expertise in fields other than weed
science participated in the tours (Table 21).
108
Table 21. Participants of the 1986 herbicide demonstration
tours and their respective presentations.
Name
Title of Presentation
Dr. Loren Wiesner
MSU Plant and Soil Science Dept.
Effect of clipping on
alfalfa seed yield
Dr. Gary Jensen
Cooperative Extension Service
Identification of
insect pests of alfalfa.
Russ Dapsauski
Allied Seed Inc.
Tactics for harvesting
alfalfa seed.
Dale Lundahl
Montana Dept. Of Agriculture
"Spur" a new insecticide
for use on alfalfa.
Tom Miles
North American Plant Breeders
Care of alfalfa seed
after harvest.
Larry Hicks
MSU Plant and Soil Science Dept.
Irrigation of alfalfa
grown for seed.
Jim Miller
MSU Plant Pathology Dept.
Diseases common to
alfalfa grown in
Montana
109
Table 22.
Testing herbicides applied early in the spring to
dormant alfalfa grown for seed.
Knudsen F a r m s . Malta, Mt.
Herbicide Application Information:
Date
Sprayer
Propellent
Time
Wind Speed
Direction
3—8—86
Backpack
. .
Pressure
Volume
Nozzles
Re l . Humidity
Air Temp.
Soil Temp.
C02
10:30 am
0-8 km/h
West
241 kPa
335 L/ha
8004
65%
5 C
2"-0.4 C
4"-0.4 C
Soil Information:
Soil type
Organic Matter
pH
46% clay
3 .2 %
8.0
Rating Information:
Date
Rated by
Crop Stage
Rating Method
6-13-86
Stannard ■
Early Flowering
Visual, 0= no control, 100= complete kill
Weeds Present
Common Milkweed
Volunteer Grain
Kochia
Canada Thistle
Prickly Lettuce
Common Lambsquarters
Annual Sunflower
Field Bindweed
Dandelion
Notes:
i
Stage of Growth
61 cm
41 cm
36 cm
41 cm
41 cm, early bud
2 leaf
4I cm, early bud
Mature, pre-bud
Mature
No herbicide was applied in 1985 to the crop.
I IO
Table 23.
Testing herbicides applied early in the spring to
dormant alfalfa grown for s e e d . Knudsen F a r m s . M a l t a , MT.
Percent Control
Trt Chemical
No. Name
I
2
3
4
5
6
7
8
9
Propham
Pronamide
Simazine
Hexazinone
Hexazinone
Terbacil
Netribuzin
Oiuron
Hexazinone +
Oiuron
10 Check
Trade
Name
Rate Alfalfa Common Volunteer
Canada
(kg/ha) Injury Milkweed Grain Kochia Thistle
Chemhoe
3.3
Kerb
1.7
Princep
1.3
Velpar
0.8
Velpar
1.1
Sinbar
0.9
Sencor/Lexone 1.1
Karmex
1.8
Velpar +
1.1
Karmex
1.8
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
20
100
30
35
90
90
86
40
20
0
30
35
30
35
100
50
0
0
0
0
20
0
0
0
0
0
0
0
68
0
63
0
0
0
Percent Control
Chemical
Name
Propham
Pronamide
Simazine
Hexazinone
Hexazinone
Terbacil
Metribuzin
Oiuron
Hexazinone +
Oiuron
10 Check
Trade
Name
Chemhoe
Kerb
Princep
Velpar
Velpar
Sinbar
Sencor/Lexone
Karmex
Velpar +
Karmex
Prickly
Annual
Field
Rate
(kg/ha) Lettuce Sunflower Bindweed
3.3
1.7
1.3
0.8
1.1
0.9
1.1
1.8
1.1
1.8
Common
Dandelion
0
0
13
100
100
70
73
73
8
0
27
100
73
47
70
20
0
0
0
0
0
0
0
0
0
0
0
0
0
20
100
0
87
0
0
0
0
Table 24.
Testing herbicides applied late in the fall to
dormant alfalfa grown for seed. Gary Wiltse River Farm, Miles
City, MT.
Herbicide Application Information.:
Date
Sprayer
Propellent
Time
Wind Speed
Direction
11-16-85
Backpack
CO2
11:00 am
0-3 km/h
South
Pressure
Volume
Nozzles
Rel. Humidity
Air Temp.
Soil Temp.
276 kPa
184 L/ha
8002
56%
7.8 C
2"-0.6 C
4"-2.2 C
Soil Information:
Soil type
Organic Matter
pH
.
17% clay .
1.8%
8.4
Rating Information:
Date
Rated by
Crop Stage
Rating Method
Weeds Present
Kochia
Field Bindweed
Green Foxtail
Russian Thistle
Notes:
6 12-86
-
Stannard
Early Flowering
Visual, 0= no control, 100= complete kill
Stage of Growth
41 cm
Mature, pre-bud
I leaf
5-10 cm,
Herbicides were sprayed 1-2 hours prior to a
shower followed by 5 cm of snow.
Metribuzin
crop.
at 1.1 kg/ha was applied in 1985 to
rain
the
Table 25. Testing herbicides applied late in the fall to
dormant alfalfa grown for seed. Gary Wiltse River Farm, Miles
City, Mt
Percent Control
10
Chemical
Name
Trade
Name
Propham
Pronamide
Simazine
Hexazinone
Hexazinone
Terbacil
Netribuzin
Oiuron
Hexazinone +
Oiuron
Check
Chemhoe
Kerb
Princep
Velpar
Velpar
Sinbar
Sencor/Lexone
Karmex
Velpar +
Karmex
Rate
Alfalfa
(kfl/ha) Injury
3.3
1.7
1.3
0.8
1.1
0.9
1.1
1.8
1.1
1.8
Kochia
Russian
Thistle
Green
Foxtail
Field
Bindweed
0
0
0
0
0
0
0
0
8
7
55
87
50
97
75
32
8
7
50
47
63
67
50
27
70
90
67
97
87
100
55
87
0
0
0
3
0
3
0
0
0
0
100
0
70
0
83
0
0
0
I I3
Table 26.
Testing herbicides applied early in the spring to
dormant alfalfa grown for seed.
John Wold Farm, L a u r e l , MT.
Herbicide Application Information:
Date
Sprayer
Propellent
Time
Wind Speed
Pressure
Volume
Nozzles
Rel. Humidity
Air Temp.
Soil Temp.
3—5—86
Backpack
CO
8:00 am
0
255 kPa
179 L/ha
8002
85%
4.4 C
2"-3.3 C
4"-2.2 C
Soil Information:
Soil type
.Organic Matter
pH
41% clay
2.9 %
8.2
Rating Information:
Date
Rated by
Crop Stage
Rating Method
Weeds Present
Canada Thistle
Field Bindweed
Common Dandelion
Quackgrass
White Clover
Note:
6 11-86
-
Stannard
Early Flowering
Visual, 0= no control, 100= complete kill
Stage of Growth
46 cm
Mature, pre-bud
Mature
Early seed fill
Flowering
Metribuzin at 1.1 kg/ha was applied in 1985 to the crop.
I 14
Table 27. Testing herbicides applied early In the spring to
dormant alfalfa grown for seed. John Wold Farm, Laurel, MT.
Percent Control
Trt Chemical
No. Name
I
2
3
4
5
6
7
8
9
10
Propham
Pronamide
Simazine
Hexazinone
Hexazinone
Terbacil
Netribuzin
Diuron
Hexazinone +
Oiuron
Check
Trade
Name
Cheehoe
Kerb
Princep
Velpar
Velpar
Sinbar
Sencor/Lexone
Karmex
Velpar +
Karmex
Rate
Alfalfa Canada
Field
(kg/ha) Injury Thistle Bindweed Quackgrass
3.3
1.7
1.3
0.8
1.1
0.9
1.1
1.8
1.1
1.8
Common
White
Dandelion Clover
0
0
3
I
2
2
11
0
0
0
7
67
63
57
57
17
0
0
0
0
0
0
0
0
3
100
80
93
100
100
100
10
3
0
70
50
93
40
100
33
0
0
100
100
100
100
100
15
3
0
37
0
3
0
100
0
100
0
100
0
APPENDIX B
Herbicide guide for alfalfa and other forage legumes
116
ALFALFA AND OTHER FORAGE LEGUMES
HERBICIDE
APPLICATION AND
REMARKS
ANNUAL GRASS AND BROADLEAF NEED CONTROL WHILE ESTABLISHING
NEW STANDS
* 2,4-DB
sold as an ester formulation under the trade name
BUTYRAC ESTERtmand as an amine formulation under
the trade names BUTYRACtm, BUTOXONEtm, 2,4-DB
BUTYRIC WEED KILLERt m , and 2,4-DB 175 HERBICIDEt m .
CROPS:
Alfalfa, clover and birdsfoot trefoil.
RATE:
2 to 6 pts/A of 2 lbs. a.e./gal amine formulation
or 2 to 4 pts/A of 2 lbs a.e./gal ester
formulation
TIME:
Apply postemergence in spring or fall to small
seedling weeds less than 3 inches tall after
legume seedling have reached the I to 2 trifoliate
leaf stage.
REMARKS
Controls only broadleaf weeds. Use the higher
rate in dry, low-humidity areas.. The use of 2,4DB is progressively more damaging to alfalfa as it
matures. Certain annual weeds such as kochia and
Russian thistle are resistant.
Labels vary
slightly, consult appropriate product label before
using.
CAUTION
Delay irrigation for 10 days after application or
injury may result.
Some crop injury can be
expected, typically stem twisting and leaf
malformation. Do not apply if the crop is
stressed.
Do not spray when daytime temperatures
are expected to exceed 90 F within the next 2 or 3
days or when temperatures are likely to fall below
40 F during or shortly after treatment. Do not
graze or feed new seedings for 60 days after
treatment.
117
c Bonofin sold under the trade name BALANtm.
CROP:
Pure stands of alfalfa, clover or blrdsfoot
trefoil.
RATE:
2 to 2.5 Ibs/A of 60DF.
TIME:
Apply and incorporate before seeding. May be
applied up to 3 weeks before seeding.
REMARKS
Use lower rates on coarse textured soils, higher
rates on fine soil.
Incorporate 2 to 3 inches
deep within 8 hours of application using two
passes at different angles.
CAUTION
Do not plant wheat, barley, rye or other grasses
within 10 months of treatment.
Do not plant
corn, oats and sugar beets within 12 months of
treatment.
* EPTC sold under the trade names EPTAMtm and GENEPtm.
/
CROPS:
Pure stands of alfalfa, clover or blrdsfoot
trefoil.
RATE:
2.25 to 4.5 pts/A of 7E or 30 to 40 Ibs/A of 10G.
TIME:
Apply and incorporate before seeding.
REMARKS
Use lower rate on sandy soils, higher rate on
silty and clay soils and for quackgrass
suppression.
Incorporate immediately 2 to 3
inches deep using two passes at different angles.
CAUTION
Temporary crop injury may occur. Do not use if a
grass or grain companion crop is to be planted with the
legume.
118
* Trlfluralin sold under the trade name TREFLANtm
CROPS:
Pure stands of alfalfa.
RATE:
I to 1.5 pts/A of 4E.
TIME:
Apply and incorporate before seeding.
REMARKS
Use the lower rate on coarse soils, higher rate on
fine soils.
Incorporate 2 to 3 inches deep within
24 hours of application using two passes at
different angles.
. CAUTION
Temporary crop injury may occur. Do not plant
sugar beets within 12 months of a spring
application or within 14 months of a fall
application. Plow the land 12 inches deep before
planting sugar beets.
Do not plant proso millet,
corn or oats within 14 months ofa spring
application or within 16 months of a fall
application. Do not seed a grass or grain
companion crop with the alfalfa
6
WINTER ANNUAL GRASSES AND VOLUNTEER CEREAL CONTROL IN NEW OR
ESTABLISHED STANDS
* Chlorpropham sold under the trade name FURLOEtm
CROPS:
Pure stands of alfalfa, birdsfoot trefoil, and
clover.
RATE:
2 to 4 qts/A of 4E.
TIME:
Apply in late fall or early spring.
REMARKS
Use on late summer seeded or established stands.
Crop must have at least 4 true leaves. Use lower
rate on coarse textured soils.
119
CAUTION
Do not harvest or graze within 40 days of
treatment. This treatment will injure or control
all annual grass species.
* Propham sold under the trade name CHEMHOEtm .
CROPS:
Pure stands of alfalfa and clover.
RATE:
3 to 4 qts/A of 4L
TIME:
Apply in late fall or early spring.
or
27 to 35 Ibs/A of 15G.
REMARKS
Crop must have at least 3 true leaves.
Use lower
rate on coarse textured soils. Rainfall or
irrigation is necessary soon after application.
Germinating and seedling plants are controlled
more readily than larger ones.
CAUTION
Do not apply when temperatures are above 60F, as
propham is rapidly lost. Apply to trash-free
alfalfa: trash interferes with chemical activity
and reduce weed control.
Do not harvest or graze
within 8 days of treatment.
This treatment will
injure or control all annual grass species.
PERENNIAL GRASSES (INCLUDING QUACKGRASS), VOLUNTEER CEREALS
AND ANNUAL GRASS CONTROL IN NEW OR ESTABLISHED STANDS
* Pronamide sold under the trde name of KERBtm .
CROPS:
Pure stands of alfalfa, clover, birdsfoot trefoil,
crown vetch and sainfoin.
RATE:
I to 4 Ibs/A of SOW.
TIME:
Apply in fall (late September through October)
before soil freezeup.
120
REMARKS
Apply to new stands after the crop has reached the
first trifoliate stage of growth. Apply to
established stands after last cutting.
Rate
depends on weed species, type of irrigation used
and dependability of rainfall. Use the higher
rates for perennial grass control. Optimal
activity occurs when applications are made under
cool conditions (55F or less) and are followed by
rainfall or overhead irrigation.
Lower rates of
application are effective for foxtail barley
control.
CAUTION
Do not harvest or graze alfalfa within 25 days of
treatment if less than 3 Ibs/A is used or within
45 days if 3 to 4 Ibs/A is .used. Do not harvest
or graze other forage legumes within 120 days of
treatment.
6 Sethoxydim sold under the trade name POASTt m .
CROPS:
Pure stands of alfalfa.
RATE:
I to 2 1/2 pts/A of I.SEC.
crop oil concentrate.
TIME:
Apply anytime to actively growing grasses when
they are at the proper stage specified on the
product label.
Always add 2 pts/A
REMARKS
Rate depends on weed size and.species.
Do not
apply to grasses under moisture or temperature
stress.
Provides poor control of downy brome
(cheatgrass), overwintering volunteer cereals and
foxtail barley. Heavy quackgrass infestations may
require a split application for complete
suppression.
Poast is most effective on grasses
before they have been cut. Where grass weeds have
been cut, apply after they grow past the minimum
height indicated on the product label. Alfalfa at
all stages of growth is tolerant to Poast.
121
CAUTION
Do not apply Poast within 7 days of feeding,
grazing or harvesting forage, or within 20 days of
feeding or harvesting hay. Do not apply more than
5 pts/A in one season. Do not apply if rainfall
is expected within one hour following application.
SUMMER ANNUAL GRASS CONTROL INCLUDING GREEN FOXTAIL
(PIGEONGRASS) IN ESTABLISHED STANDS
0 Trifluralin sold under the trade name TREFLANt m .
CROPS:
Pure stands of alfalfa.
RATE:
2.0 qts/A of 4MTF or 20 Ibs/A of TR-IO G .
TIME:
Apply anytime before weeds germinate when the
ground is not frozen.
REMARKS
Treflan must be activated by a single
rainfall or overhead sprinkler irrigation of 0.5
inch within 3 days after application, or
mechanical equipment that will ensure thorough
soil mixing with minimum damage to the alfalfa.
This treatment will not control emerged weeds.
CAUTION
Where established alfalfa is to be rotated to
another crop the year following application, plant
only those crops for which Treflan can be applied
as a labeled preplant treatment or injury may
result/ This is a specialized treatment and
trifluralin should not be incorporated.
ANNUAL BROADLEAF WEED CONTROL IN ESTABLISHED STANDS
* MCPA amine sold under several trade names
CROPS:
Pure stands of alfalfa.
122
RATE:
I pt/A of 4 lbs a.e./gal amine formulation.
TIME:
Apply in late fall to dormant alfalfa.
REMARKS
Controls winter annual broadleaf weeds. Labels
vary slightly, consult appropriate product label
before using.
CAUTION
Non-dormant alfalfa will be injured.
* 2,4 DB
sold as an ester formulation under the trade name
BUTYRAC ESTERtm and as an amine formulation under
the trade names BUTYRACtm, BUTOXONEtm, 2,4-DB
BUTYRIC WEED KILLERtm , and as 2,4-DB 175
HERBICIDEtm.
CROPS
Alfalfa, clover and birdsfoot trefoil.
RATE:
2 to 6 pts/A of 2 lbs a.e./gal amine formulation
or 2 to 4 pts a.e./A of 2 Ibs/gal ester
formulation.
TIME:
Apply postemergence in spring or fall to small
seedling weeds less than 3 inches tall.
REMARKS
Use the higher rate in dry, low-humidity areas.
The use of 2,4-DB is progressively more damaging
to alfalfa as it matures. Certain annual weeds
such as kochia and Russian thistle are resistant.
Labels vary slightly, consult appropriate product
label before using.
CAUTION
Delay irrigation for 10 days after application or
injury may result. Some crop injury can be
expected, typically stem twisting and leaf
malformation.
Do not apply if the crop is
stressed.
Do not spray when daytime temperatures
are expected to exceed 90 F within the next 2 or 3
days or when temperatures are likely to fall below
40 F during or shortly after treatment.
123
ANNUAL GRASSES AND BROADLEAF WEED CONTROL IN ESTABLISHED
STANDS
# Dluron sold as KARMEXtm OR DIREXtm.
CROPS:
Pure stands of alfalfa and sainfoin.
RATE:
For alfalfa apply 1.5 to 3 Ibs/A of SOW.
sainfoin apply 2 Ibs/A of SOW.
TIME:
Apply in late fail or early spring to dormant
alfalfa stands. Apply in,fall to dormant sainfoin
stands.
For
REMARKS
Use on alfalfa and sainfoin stands established, at
least one year. Not very effective on downy brome
(cheatgrass) or volunteer cereals. Rates vary
according to weed species. Use higher rates on
fine textured soils or soils high in organic
matter.
CAUTION
Do not apply to snow-covered or frozen soil. Do
not use on sand or loamy sand soils or soils with
less than 1% organic matter. Do not replant
treated area within two years after application.
e Paraquat sold as CYCLONEtm OR GRAMOXONE SUPERt m .
CROPS:
Pure stands of alfalfa and clover.
RATE:
0.5 to 0.75 lb a.i./A of 1.5 or 2.0 lbs a.i./gal
formulation. Add a high quality nonionic
surfactant at 8 to 32 oz/100 gal spray mix.
TIME:
Apply after last cutting in fall or in spring to
dormant established stands before regrowth is more
than 2 inches tall.
k
REMARKS
Apply after weeds have emerged and before they are
over 6 inches tall.
Control decreases as weed
124
size increases.
Use 20 or more gals. of water
carrier per acre for ground application.
CAUTION
A RESTRICTED-USE HERBICIDE. Do not graze treated
fields before first cutting.
Do not harvest or graze
within 60 days of treatment for clover or 42 days
of treatment for alfalfa.
Do not apply more than
once per season. Follow safety precautions on the
label.
ANNUAL GRASSES AND BROADLEAF WEED CONTROL AND SUPPRESSION OF
CERTAIN PERENNIAL WEEDS IN ESTABLISHED STANDS
» MetribUZin sold as SENCORtm or LEXONEtm.
CROPS:
Alfalfa and sainfoin, pure or mixed stands with
grasses.
RATE:
0.75 to 2 pts/A O^ 4L, or
75DF.
TIME:
Apply in late fall or early spring to dormant
stands.
0.5 to 1.33 Ibs/A of
REMARKS
Use on stands established at least 12 months.
The Sencor and Lexone labels differ slightly;
consult the appropriate label for the product
used. Rates vary according to weed species. Use
the higher rates on fine textured soils, soils
high in organic matter and for quackgrass control.
Forage grasses are injured at higher rates.
CAUTION
Even when used as directed, stunting and chlorosis
may occur under stress conditions such as low
fertility, disease, overcutting, drought or frost.
Do not apply to frozen soil. Do not use on sands
or soils with less than 1/2% organic matter. Do
not use Sencor on soils with a pH greater than
7.5. Do not harvest or graze within 28 days of
treatment.
Consult label recropping
recommendations.
125
* Slmazlne sold as PRINCEPtm OR SIMAZINE SOWtm .
CROPS:
Pure stands of alfalfa.
RATE:
I to 2 Ibs/A of SOW or 0.9 to 1.75 Ibs/A of 90DF.
TIME:
Apply in late fall or early spring to dormant
stands.
REMARKS
Use on stands established at least 12 months.
Higher rates will suppress quackgrass but not
consistently.
CAUTION
Even when used as directed stunting and chlorosis
may occur under stress conditions such as low
fertility, disease, overcutting, drought or frost
Do not apply to frozen soil. Do not use. on soils
with less than 1% organic matter or on soil with
pH 7.8 or above.
Do not use on sand, loamy sand
or gravelly soils.
Do not graze treated areas
within 30 days or harvest within 60 days of
treatment. Do not plant any crop except corn the
year after application or injury may occur. High
soil pH increases herbicide persistence.
* Terbacil sold as SINBARt m .
CROPS:
Pure stands of alfalfa.
RATE:
0.5 to 1.5 Ibs/A of 80W.
TIME:
Apply in late fall or early spring to dormant
stands.
REMARKS
Use on stands established at least 12 months.
Use
the lower rate on coarse, sandy soils or soils low
in organic matter.
CAUTION
Not labeled for use on alfalfa grown for seed in
Montana.
Do not use on sand, loamy sand or
gravelly soil. Do not use on soils with less than
126
1% organic matter. Do not apply on snow-covered
or frozen ground. Do not replant treated areas to
any crop within 2 year after last, application.
PERENNIAL WEED CONTROL - QUACKGRASS, FIELD BINDWEED, CANADA
THISTLE, ETC.
* Glyphosate sold as ROUNDUPtm.
,
CROPS:
Alfalfa and other forage legumes.
RATE:
3 to 5 qts/A or 2% solution (2.5 fluid ounces per
gallon of spray solution) for spot treating with a
hand sprayer.
TIME:
Apply preplant or for spot treatment in crop.
Refer to label for growth stages of perennial
weeds.
REMARKS
Do not till for 7 days following preplant
applications.
Spot treatments made in crop will
kill the crop in the treated area.
Do not treat
more than one-tenth of any one acre at one time
and do not harvest or graze within 14 days of
application when spot treating perennial weeds in
crop.
CAUTION
Do not apply if weed is under weather stress.
Rainfall occuring within 6 hours after application
may reduce effectiveness.
Table 28.
Weed response to herbicides applied to
and other forage legumes.
NEED SPECIES
8
A
L
A
N
C
A
R
B
Y
N
E
G
G
P
G
P
P
P
F
F
G
F
G
G
G
P
F
P
P
P
C
H
E
M
F
U
R
L
0
E
G
R
A
M
0
X
0
N
E
K
A
R
M
E
X
K
E
R
B
G
G
G
P
P
P
F-G
F
G
G
G
G
G
G
F
G
G
F
H
0
E
4D
B
E
PG
I E
AN
HE
P
P
P
P
P
P
P
P
P
G
P
P
P
G
G
P
P
P
G
G
P
P
P
P
P
P
P
P
P
P
P
G
G
P
G
P
F
F
G
G
G
G
G
F
P
P
P
F
F
G
F
F
F
G
P
P
P
F
F
F
P
P
P
P
P
P
P
P
P
P
P
P
P
P
P
P
P
P
G
G
G
G
G
G
G
P
G
F
F-G
FG
F-G
FG
P
P
F
P
P
F
P
P
P
P
F
F-G
P
F
F
G
G
G
F
F
F
F
2,
alfalfa
T
R
I
S
E
NL
CE
0X
R0
N
E
F
P
0
A
S
I
P
R
I
N
C
E
P
R
L
U
R
A
L
I
N
G
G
G
G
G
G
G
F-G
G
G
G
G
G
P-F
P
G
G
F-G
G
G
C
G
G
F
F
P
G
G
G
F
F
G
G
F-G
F-G
F
F
F
F
G
G
G
G
FG
F
G
G
G
G
G
P
G
P
P
P
F
F
G
F
F
F
F
P
F
G
P
P
P
P
P
P
P
P
P
P
P
G
G
G
G
G
G
G
G
G
G
F
G
G
G
G
G
G
F
F-G
F
G
G
G
G
G
F
G
F
F-G
G
G
P
G
P
P
P
S
I
N
B
A
GRASSY WEEDS
-
BROADLEAF WEEDS
Annuals
Kochia
Lambsquarters
Pigweed, prostrate
redroot
Prickly lettuce
Russian thistle
Shepherdspurse
Wild buckwheat
Wild sunflower
127
Annual foxtails
Barnyardgrass
Bulbous bluegrass
Downy brome
Foxtail barley
Quackgrass
Smooth broeegrass
Volunteer grain
Wild oats
Wltchgrass
Table 28 cont'd
WEED SPECIES
B
A
L
A
N
C
A
R
B
Y
N
E
P
P
P
P
P
P
P
P
P
P
P
P
P
P
C
H
E
M
H
0
E
2.
4D
B
E
PC
I E
AN
HE
P
P
P
P
P
P
P
P
F
P
F
P
P
F
G
P
P
P
P
P
P
P
F
U
R
L
0
E
G
R
A
M
0
X
0
N
E
P
P
P
P
P
P
P
P
P
P
P
P
F
F
K
A
R
H
E
X
P
P
P
P
P
P
P
K
E
R
B
P
0
A
S
T
P
R
I
N
C
E
P
S
E
NI
CE
0X
R0
N
E
S
I
N
B
A
R
I
R
I
F
L
U
R
A
L
I
N
P
P
P
P
P
P
P
P
P
P
P
P
P
P
P
P
P
P
P
F
P
P
F
F-G
P
P
F
P
P
F
F
P
P
F
P
P
P
P
P
P
P
P
BlennUls and
Perennials
Canada thistle
Curly dock
Dandel ion
Field bindweed
Milkweed
Salsify
Sweet clover
G - Good; F » Fair;
P - Poor
Response of weeds to any of the listed herbicides may be altered by growing conditions, weed populations,
type of irrigation, genetic variations of weeds, soil type, pH, organic matter, time of application and
application rates. Ratings may vary from season to season and geographic areas. Weed control generally
decreases as the season progresses.