WEED MANAGEMENT CONCEPTS:
Developing Native Forb Seed Production
Strategies
Corey Ransom
Methods of Weed Control
•
•
•
•
•
Preventative
Biological
Cultural
Mechanical
Chemical
Preventive Weed Control in Row Crops
•
•
•
•
•
Clean equipment (planting, cultivating, harvest)
Clean field borders
Weed screens for irrigation water
Prevention of weed seed production
Spot treatment
Cultural Control
•
•
•
•
•
•
•
•
•
Crop rotation
Site selection
Stale seedbed
Seedbed preparation
Proper planting date/depth/conditions/density
Competitive varieties/disease resistant/vigor
Disease and insect management
Fertility management/placement
Irrigation management – Drip?
Physical and Mechanical Control
•
•
•
•
•
•
•
Preplant Tillage or Cultivation
Preemergence Cultivation
In Crop Cultivation
Blind Cultivation
Mulches
Flaming (nonselective/selective)
Handweeding
Opportunities to innovate
cultivation tools
Hand weeding intra-row weeds
Time consumption for hand
weeding
Crop
Hour/ha
Onion
sown
100-400
Carrot
sown
100-400
Sugarbeet
sown
80-150
Transplants
20-50
DIAS
Chemical Weed Control
Few herbicides that could
currently be legally used to
control weeds in native forb
seed production.
We need to identify and label
herbicides that can be used
to selectively control weeds
in our forb seed crops.
Herbicide Selectivity
Definition
- a treatment that at a given dosage is toxic
to some plant species but does not
damage others.
Herbicide Selectivity
Mechanisms (Physical):
1. Timing of herbicide application relative to crop
growth (Roundup while crop is dormant)
2. Herbicide placement relative to:
- Pattern of crop growth and development
- Contact with plants (banding, drop nozzles)
Herbicide Selectivity Through
Placement/Timing
Selective Placement
Hooded band sprayer
- can shield spray or plant
- generally use herbicide that
is not systemic
www.wyliespraye rs.com
Herbicide Selectivity
Mechanisms (Physiological):
1.
2.
3.
4.
Differential
Differential
Differential
Differences
absorption (includes retention)
translocation.
metabolism.
in sensitivity at the target site.
Herbicide Selectivity Due to Plant Physiology
Physiological – differences in plant growth
Herbicide Selectivity Due to Plant Physiology
Physiological – Differences in plant growth
Ex. Contact herbicides in perennial crops.
Objective – Herbicides for Seed Production
Identify herbicides for
weed management in
forb seed production.
- Basalt milkvetch
- Western prairie clover
- Searls’ prairie clover
- Tapertip hawksbeard
Initial Preemergence Herbicide Screen
-50 seeds per flat.
-50/50 Sandy Loam Soil with peat
and vermiculite potting soil.
-sprayed in chamber at 20 gpa.
-Crepis stored at 34 F for 3 weeks.
-evaluated 4 weeks after treatment.
Species:
- Basalt milkvetch
- Western prairie clover
- Searls’ prairie clover
- Tapertip hawksbeard
Preemergence Herbicides and Rates
Kerb
1.0
Treflan
0.375
Prowl H2O
0.75
Outlook
0.656
Sencor
0.375
Plateau
0.0625
Olympus
0.0267
Chateau
0.047
Tapertip Hawksbeard Symptoms
Kerb
Untreated
Sencor
Olympus
Treflan
Prowl H2O
Plateau
Basalt Milkvetch Symptoms
Prowl H2O
Outlook
Sencor
Olympus
Treflan
Kerb
Western Prairie Clover Symptoms
Prowl H2O
Outlook
Untreated
Treflan
Olympus
Postemergence Herbicide Screening, 2009
Conducted on fields established in
2005 as transplants from conetainers.
Plants were spaced 0.5 m.
Herbicide treatments applied May 12,
15, and 21, 2009.
Applications made with a shielded
bicycle sprayer at 20 gpa and 30
psi.
Multiple accessions and inconsistent
plant vigor prior to treatment add
to variability in these trials.
Herbicide Treatments on Basalt Milkvetch
Herbicide
Rates
lb ai/A
product
Buctril
0.25
1.0 pt
2,4-DB
0.25
1.0 pt
Transline
0.124
0.33 pt
Paramount + MSO
0.248
0.33 lb
Raptor + MSO
0.078
10.0 oz
MSO at 1.0% v/v
• Application made May 15.
• Injury evaluated May 26 (11 DAT) and June 23 (41 DAT).
• Biomass taken July 23.
Basalt Milkvetch Injury on May 23 and June 25
70
60
11 DAT
41 DAT
Injury (%)
50
40
30
20
10
0
Buctril
2,4-DB
Transline
Paramount
Raptor
Treatment
• Transline again caused significant season long injury
• 2,4-DB , Paramount, and Raptor had among the least injury
Milkvetch Plant Weight in Response to Herbicides
25
a
Biomass (g/plant)
20
15
a
a
a
b
10
b
5
0
Untreated
Buctril
2,4-DB
Transline Paramount Raptor
Treatment
• Buctril and Transline significantly reduced plant biomass.
Millkvetch Flowering in Response to Herbicides
12
a
Flowering (plants/plot)
10
8
6
ab
4
bc
bc
2
bc
c
0
Untreated
Buctril
2,4-DB
Transline Paramount Raptor
Treatment
Herbicide Injury in Basalt Milkvetch
Herbicide Treatments on Western Prairie Clover
Herbicide
Rates
lb ai/A
product
Prowl H2O
0.71
1.5 pt
Outlook
0.84
18.0 oz
Goal
0.25
0.66 lb
0.064
1.0 pt
Sencor + NIS
0.5
0.66 lb
Buctril
0.25
1.0 pt
2,4-DB
0.25
1.0 pt
Transline
0.124
0.33 pt
Paramount + MSO
0.248
0.33 lb
Raptor + MSO
0.078
10.0 oz
Milestone
0.047
3.0 oz
Chateau + NIS
NIS at 0.25% v/v
MSO at 1.0% v/v
• Applied May 21.
• Injury evaluated
May 26 (5 DAT) and
June 25 (35 DAT).
• Plant biomass and
seed head biomass
August 6.
Western Prairie Clover Response to Herbicides
Injury
Herbicide
5 DAT
Biomass
35 DAT
----------------%--------------
Veg.
Seed head
----------g/plot----------
Untreated
-
-
520
243
Prowl H2O
10
1
545
203
6
4
616
189
Goal
64
26
513
218
Chateau + NIS
56
18
479
203
Sencor + NIS
21
5
571
140
Buctril
13
14
337
126
2,4-DB
23
10
393
150
Transline
41
44
416
32
Paramount + MSO
25
10
704
191
Raptor + MSO
38
18
446
185
Milestone
35
63
257
2
Outlook
Herbicide Injury in Prairie Clover
Impact of Application Timing
• No herbicide injury was
evident in 2008 when
applications were made while
prairie clover was dormant.
• Significant injury appeared
when actively growing prairie
clover was treated in 2009.
Issue of crop selectivity vs.
weed efficacy.
Conclusions – Seed Production
1. 2,4-DB warrants further investigation for
postemergence use in basalt milkvetch.
2. Established western and Searls’ prairie clover
appear to tolerate postemergence treatments of
several herbicides, but impact on seed yield and
viability has not been determined.
3. Transline and Milestone is too injurious for potential
use.
4. Likely, the use of soil active herbicides will continue
to cause minimal damage to established plants.
Herbicides That Could Have Great Utility
1. Graminicides – Poast, Select, etc.
2. Preemergence herbicides used in established
plantings - Prowl, Outlook
3. Preemergence soil active herbicides for
establishment?
4. Postemergence herbicides – Contact and Nonselective
5. Postemergence herbicides – Selective
Where Do We Go From Here?
Need to have herbicides registered for use in native
seed crops.
1. Small acreage high value crops
2. Require “Third Party” indemnification label
3. Who will hold the label?
USDI BLM Great Basin Restoration
Initiative, GBNPSIP, and
USDA FS Rocky Mountain Research
Station