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CONTROL OF VOLUNTEER SOYBEANS IN CORN
Travis D. Courtney
Biography
Grew up in Texas with cotton, corn, and grain sorghum
Worked for Monsanto since 2001
Worked in South Dakota with soybeans
Currently in Kansas working with corn and soybeans
Married with one daughter Enjoy the outdoors in my
down time – hunting, fishing, camping and golf
Introduction
With world populations climbing higher and higher farmers are expected to produce more on less acres
Corn is a vital grain that contributes to many industries from food to fuel, cosmetics to industrial materials
Corn yields are directly linked to good weed control Volunteer soybeans not typically seen as competitive
to corn crops, but can be in certain situations Soybeans are resistant to several modes of action
and active ingredients
Objectives
Determine which chemicals can be effective at controlling volunteer soybeans
Determine pre-emerge (PRE) and post-emerge (POST) options
Use herbicides already available to producers which can be incorporated into current herbicide programs
Test herbicides over several soil types and environments
Materials and MethodsLocation Specifics
Location Soil Series Tillage Clay %Organic
Matter %pH
Harrisburg, SD
Wentworth Silty Clay
Loam
Conventional – fall and
spring30 4
7.0 or slightlybelow
Leland, MSCommerce Fine-Silty
Loam
Conventional – fall and
spring30 2.3
7.0 or slightly above
Mt. Olive, NCKenansville loamy sand
Conventional – fall and
spring6 1.3 5.3
Materials and MethodsLocation Specifics cont.
Harrisburg Planted with
planter AG2031 soy DKC 49-29 SSRIB
corn
Leland Planted with
planter AG4632 soy DKC 64-87 SSRIB
corn
Mt. Olive Planted by hand AG5605 soy DKC 62-08 SSRIB
corn
R15‐16 Rep 2R13‐14 Rep 2R11‐12 Rep 2R9‐10 Rep 2R7‐8 Rep 1R5‐6 Rep 1R3‐4 Rep 1R1‐2 Rep 1
R7‐8 Rep 1
R5‐6 Rep 1
R3‐4 Rep 1
R1‐2 Rep 1
R15‐16 Rep 2R13‐14 Rep 2R11‐12 Rep 2R9‐10 Rep 2R7‐8 Rep 1R5‐6 Rep 1R3‐4 Rep 1R1‐2 Rep 1
Materials and MethodsApplication
SprayDesign.xlsx Target Corn Application Stage – V4-V6 Target Soybean Application Stage – V2-V3 CO Backpack Sprayer
with 10’ boom Herbicides applied at label
rates, 20 gallons/acre sprayvolume, 40 psi, and 3.0 mph
Materials and MethodsRatings
Soybean “control” = soybean death Stand counts – emergence and control 28 days after treatment for PRE and POST Herbicide damage to corn if seen
Materials and MethodsHerbicides
PRE 1. TripleFlex - (acetochlor+flumetsulam+clopyralid)2. Resolve Q - (rimsulfuron+thifensulfuron)3. Atrazine 4F - (atrazine)
POST1. RoundUp Weathermax - (glyphosate)2. Capreno - (thiencarbazone+tembotrione)3. Liberty - (glufosinate)4. Resolve Q - (rimsulfuron+thifensulfuron)5. TripleFlex - (acetochlor+flumetsulam+clopyralid)6. WideMatch - (clopyralid+fluroxypyr)
Materials and MethodsHerbicides cont.
PRE Herbicide Treatments
Active Ingredient (AI)Product
rate/AcreAI/Acre
(lbs)
Corn Timing
Soybean Timing
glyphosate (control) 22 oz 0.95
After planting but prior
to emerging
After planting but
prior to emerging
atrazine 2 pt 1.0
rimsulfuron+thifensulfuron
1.25 oz (wt)
2.88, 0.64
acetochlor+flumetsulam+ clopyralid
2 pt0.94, 0.03, 0.095
Materials and MethodsHerbicides cont.
POST Herbicide Treatments
Active Ingredient (AI)Product
rate/AcreAI/Acre
(lbs)
Corn stage of
development at
application
Soybean stage of development at application
glyphosate (control) 22 oz 0.95
V4-V6 V3-V4
thiencarbazone+tembotrione3 oz 0.013,
0.068glufosinate 22 oz 0.40
rimsulfuron+thifensulfuron1.25 oz (wt) 2.88,
0.068
acetochlor+flumetsulam+clopyralid2 pt
0.94, 0.03, 0.095
clopyralid+fluroxypyr1.33 pt 0.125,
0.125
Results and Discussion
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
1.8
2
6/1 6/11 6/21 7/1 7/11 7/21 7/31
Harrisburg, SD Precipitation
Precipitation (inches)
June and July
Average = 7"Total = 4.9"Deviation = -2.1"
Final CountPlanting
Source: www.accuweather.co
PRE POST
0
0.2
0.4
0.6
0.8
1
1.2
6/1 6/11 6/21 7/1 7/11 7/21 7/31 8/10
Leland, MS Precipitation
Precipitation(inches)
June and July
Average = 8.56"Total = 3.24"Deviation = -5.35
Planting
PRE POST Final Count
Source: www.accuweather.co
Results and Discussion
0
0.5
1
1.5
2
2.5
3
5/1 5/11 5/21 5/31 6/10 6/20 6/30 7/10
Mount Olive, NC Precipitation
Precipitation (inches)
May and June
Average = 7.63"Total = 13.54Deviation = +5.91
Source: www.accuweather.co
Planting/PRE
POST Final Count
Results and Discussion
Conclusion and DiscussionPRE Herbicides
Atrazine and acetochlor + flumetsulam + clopyralid showed control across locations
Herbicides did not prevent germination Control achieved with root uptake Rimsulfuron + thifensulfuron did not show control
but did severely injure soybeans
Conclusion and DiscussionPRE Herbicides
Relatively low amount of atrazine used in study; control should increase with rate increase
Herbicide carryover is a concern with atrazineand clopyralid products
Soil texture, organic matter, pH, clay content and rainfall should be considered prior to herbicide application for rates and carryover potential
Conclusion and DiscussionPOST Herbicides
Best control achieved with clopyralid + fluroxypyracross locations
Acetochlor + flumetsulam + clopyralid showed control across locations with a few escapes
Glufosinate performed well in MS and NC Thiencarbazone + tembotrione performed well in
NC Rimsulfuron + thifensulfuron showed control at 14
DAT with re-growth at 28 DAT
Conclusion and DiscussionPOST Herbicides
Clopyralid products performed excellent across locations
Avoid clopyralid use as PRE and POST due to selection pressure and maximum annual rates
Apply prior to V6 corn Carryover may be a concern with <15” rain or OM
>2% Soybeans showed herbicide damage within 24 hrs
Conclusion and DiscussionPOST Herbicides
Glufosinate performed well in more humid environments (NC and MS)
Excellent weed control list Plant glufosinate-tolerant corn hybrids Ensure volunteer soybeans are not glufosinate-
tolerant No carryover concerns
Conclusion and DiscussionHerbicide “stacks”
Stacking – multiple herbicides with varying MOAs in one application
Clopyralid and glufosinate products mix well with many herbicides, including each other
Thiencarbazone + tembotrione and rimsulfuron+ thifensulfuron control a large list of weeds and “set back” soybeans early
Will control other weeds in the field more effectively
Conclusion and DiscussionHerbicide Agronomics
PRE chemistries typically need rain, irrigation or shallow incorporation
Precipitation amounts to incorporate PRE – usually ¼-½ inch Be aware of minimum annual rainfall needed for PRE
chemistries. Crop damage can occur if these are not met. Crop rotation intervals Soil pH, texture and organic matter can disqualify some PRE
and POST chemistries Early cut-off for effective POST chemicals (V5/V6 Corn
typically) Good coverage, proper nozzles, agitation, PSI, mixing order,
etc. are all extremely important for control
Questions?