Soil Applied Residual Herbicide Affect on Conventional and Imidazolinone Resistant Canola
in the Southeastern US
Timothy Grey1, Paul Raymer2, and G. David Buntin2
1The University of Georgia, 115 Coastal Way, Tifton, Georgia, 31793-0748, tgrey@uga.edu, 21109 Experiment St. Griffin Georgia 30223
Stand counts
Pioneer 45A71
Flint
________
plants/m row_________
0
4
Diclosulam
82
63
100
14
0
5
Imazapic
18
1
96
26
3
6
Imazapic
35
1
97
24
1
7
Imazapic
71
6
100
18
1
8
Chlorimuron
2
12
57
27
20
9
Chlorimuron
4
4
71
23
19
10
Chlorimuron
9
13
83
27
13
11
Pyrithiobac
13
10
68
23
26
12
Pyrithiobac
27
9
81
27
19
13
Pyrithiobac
54
17
93
24
15
14
Trifloxysulfuron
5
8
68
22
21
15
Trifloxysulfuron
8
5
69
26
21
16
Trifloxysulfuron
13
15
81
28
16
17
Flumioxazin
26
79
79
12
9
18
Flumioxazin
53
88
91
8
5
19
Flumioxazin
108
98
98
1
3
20
Fomesafen
105
68
80
19
21
21
Fomesafen
210
82
87
10
8
22
Fomesafen
420
97
90
4
1
23
Sulfentrazone
105
84
85
13
14
24
Sulfentrazone
210
85
84
7
13
25
Sulfentrazone
280
93
89
7
12
Figure 4. PPO inhibitor injury on Pioneer 45A71 and Flint canola.
100
90
80
70
60
50
40
30
20
10
0
Herbicide rate
1/4 x
1/2 x
1x
Fli
nt
17
az
on
e
100
Su
l fe
ntr
43
P4
5A
71
41
az
on
e
Diclosulam
nF
li n
t
3
Su
l fe
ntr
1
sa
fe
23
1
99
Fo
me
21
nP
45
A7
20
sa
fe
Diclosulam
Fli
nt
2
Pioneer 45A71 and Flint canola exhibited extensive injury and
nearly complete stand failure (Table 1) and crop loss with the PPO
herbicides flumioxazin, fomesafen, and sulfentrazone (Figure 4). This
susceptibility resulted in in no or significantly reduced yields (data not
shown). For the ALS herbicides imazapic, chlorimuron, pyrithiobac,
and trifloxysulfuron, Pioneer 45A71 canola injury was 17% or less for
all rates (Figure 5) and yields were not different from the nontreated
control (Data not shown). Pioneer 45A71 exhibited excellent tolerance
to imazapic at ¼, ½, and 1x rates (Figure 2). In contrast, Flint canola
exhibited 57% injury or greater (Figures 3 & 5) and yield reductions for
imazapic, chlorimuron, pyrithiobac, diclosulam, and trifloxysulfuron at
all rates (Data not shown).
Pioneer 45A71 exhibited dose response injury of 21, 43, and 63%
for the ¼, ½, and 1x rates of diclosulam, respectively (Figure 5).
Additionally, stand was reduced from 26 to 14 plants/m row for the
nontreated check to diclosulam at 82 g/ha, respectively. This indicates
that imi-resistant canola is not resistant to all ALS herbicides which
should be considered when planning potential rotational options for
canola.
Fo
me
32
az
in
26
mi
ox
0
71
0
Flu
0
P4
5A
Nontreated
az
in
1
RESULTS AND DISCUSSION
% injury
Rate
_
g ai/ha_
mi
ox
Treatment
Herbicide/canola combination
Imazapic rate
Figure 5. ALS inhibitor injury on Pioneer 45A71 and Flint canola.
1X
t
nF
l in
su
lfu
ro
45
A7
1
Tri
flo
xy
su
lfu
ro
nP
Fli
nt
71
im
uro
n
Ch
l or
Tri
flo
xy
Fli
im
uro
n
za
pi c
Ch
l or
Im
a
P4
5A
1
5A
7
P4
za
pi c
lam
los
u
P4
5A
7
lam
los
u
Dic
Figure 3 (Top). Imazapic carryover
simulation to Flint
canola from ¼x
application rate.
nt
1/4 x
1/2 x
1x
1
Figure 1. Pioneer 45A71 (staked bed, left) and Flint (nonstaked bed, right) canola planted in Plains, GA.
Herbicide rate
Fli
nt
½X
100
90
80
70
60
50
40
30
20
10
0
Im
a
¼X
Figure 2 (Left). Imazapic carryover
simulation to Pioneer 45A71 (left bed of each
picture) and Flint (right bed of each picture) at
¼ x (top), ½ x (middle), and 1x rates (bottom).
Note dose response for Flint from ¼x to ½x
rates but no difference for Pioneer 45A71.
Dic
REFERENCES
Anonymous. 2002. Oilseed plant going to Claxton in Georgia Faces. Univ. Georgia College of Agric. & Env. Sci. at
http://georgiafaces.caes.uga.edu
Economic Research Service - U.S. Department of Agriculture (ERS-USDA). 2002. Title I, Commodity Programs in Farm
Policy, the 2002 farm bill: provisions and economic implications. at http://www.ers.usda.gov/Features/farmbill/
National Agricultural Statistics Service (NASS). 2002. National Agricultural Statistics Service U.S. Dept. of Agri.. 2000
Annual summary. NASS-USDA, Washington, DC.
Injury
Pioneer 45A71 Flint
____________ _____________
%
% injury
MATERIALS & METHODS
Experiments were conducted in Georgia during 2002-2003 at the Bledsoe Research Farm near
Williamson and in 2003-2004 and 2004-2005 at the Southwest Georgia Branch Experiment Station
located near Plains in separate areas of the same field. Soils were a Cecil sandy clay loam (clayey,
kaolinitic, thermic, Typic Hapludult) at Williamson and a Faceville sandy loam (clayey, kaolinitic,
thermic, Typic Kandiudults) at Plains. Organic matter ranged from 1.0 to 2.0% with pH from 6.0 to 6.5
at both locations. In the fall of each season, seedbeds were conventionally tilled using a moldboard
plow and smoothing with a rotary tiller. Canola was seeded with a Great Plains drill with a 19 cm row
width on October 11, 2002, November 11, 2003, and October 18, 2004 at a rate of 28 seed per m of row.
Each experiment was arranged as a split plot with treatments replicated four times. Plot size was 3.66
m wide by 7.6 m long (Figure 1). Herbicides were PRE applied with a CO2-pressurized backpack
sprayer calibrated to deliver 187 L/ha at 210 kPa. Emergence dates for all trials was approximately
one week after planting. Split plots were seeded on 1.83 m bed with imidazolinone-tolerant ‘Pioneer
45A71’ and on the other 1.83 m bed to the to conventional canola ‘Flint’. The intent was to determine
tolerance to ALS herbicides.
Screening of herbicide tolerance to two classes of herbicides was investigated. Modes of action
included acetolactate synthase inhibitors (ALS) and protoporphyrinogen oxidase inhibitors (PPO).
Five ALS herbicides and three PPO herbicides were evaluated. Factors included cultivars (IMItolerant canola and traditional canola) and herbicide rate (1x, ½x, ¼x) that resulted in 25 treatments.
Treatments included a nontreated check, the ALS herbicides diclosulam, imazapic, chloriuron,
pyrithiobac and trifloxysulfuron, and the PPO herbicides flumioxazin, fomesafen, and sulfentrazone.
(Table 1).
Crop injury was visually estimated on a scale of 0 (no injury) to 100% (death). Crop injury ratings
were taken at 140, 70, and 58 days after planting (DAP) for the 2002, 2003, and 2004 plantings,
respectively. Canola stand counts were taken 58 DAP for the 2004 planting. Plots were harvested
(2004 only) with conventional plot combine.
Table 1. Herbicide treatments for canola herbicide resistance study.
Flu
INTRODUCTION
Interest in canola quality oilseed rape, Brassica naupus L., in the southeastern US has recently
increased (Anonymous 2002) . There are several potential markets for canola in this region including:
1) whole grain exports of non-genetically modified canola, 2) newly developed specialty oil lines, 3)
improved commodity prices (ERS-USDA 2002) and 4) production uses for biodiesel. Agronomic
production of a profitable canola crop in the southeastern U.S. will depend on reliable information
about rotational restrictions to cotton, peanut, and other agronomic herbicides. Agronomic row crop
production in Georgia, Florida, Alabama, and South Carolina represent 1,005,000 hectares of cotton,
323,300 hectares of corn, 329,820 hectares of peanut, 348,030 hectares of soybean, and 25,500
hectares of tobacco (NASS, 2002). Wheat, oats, and rye, planted in winter rotations with these crops
represent 434,230 hectares (NASS, 2002). Canola integrated as part of a winter rotation, October
planted and May harvested, could potentially increase farmer profits, as an alternative oil seed crop.
Herbicides used in row crop production in the southeastern U.S. vary by crop. In the south,
imazapic and diclosulam are applied to approximately 85% of the peanut hectares. Pyrithiobac is
applied to greater than 30% of the cotton crop. Imazapic, diclosulam, and pyrithiobac mode of action
is through acetolactate synthase (ALS) inhibition. Other ALS herbicides used in these crops include
chlorimuron and trifloxysulfuron. Herbicides having different modes of action that are used in the
southeastern US in cotton and peanut include sulfentrazone, fomesafen, and flumioxazin. However,
rotational data for these herbicides for canola have not been established in the southeastern U.S.
One reason to evaluate canola for herbicide carryover in this region is the moderate temperature and
moisture regimes that can perpetuate the degradation of pesticides.
Clearfield canola cultivars have ALS resistance, specifically to imidazolinone herbicides.
Clearfield-resistant canola was marketed commercially in Canada during 1998 and is now available for
evaluation in the United States. The use of Clearfield canola could be very beneficial for canola
growers in the southeastern U.S., allowing the use of imazamox herbicide that has selective control of
wild radish (Raphanus raphanistrum L.), many other dicot weeds, and Italian ryegrass (Lolium
multiflorum Lam.) (Grey et al. 2003). Additionally, Clearfield canola potentially could be grown with
reduced risk of injury, in rotation with cotton, peanuts, and other row crops that have had ALS mode
of action herbicides (imazapic, diclosulam, pyrithiobac, etc.) applied for weed control. However,
research for tolerance to these herbicide has not been established.
Herbicide/canola combination