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?