CONTROL OF VOLUNTEER SOYBEANS IN CORN. Travis D. Courtney

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1 CONTROL OF VOLUNTEER SOYBEANS IN CORN Travis D. Courtney

2 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

3 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

4 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

5 Materials and Methods Location Specifics Location Soil Series Tillage Clay % Organic Matter % ph Harrisburg, SD Wentworth Silty Clay Loam Conventional fall and spring or slightly below Leland, MS Commerce Fine-Silty Loam Conventional fall and spring or slightly above Mt. Olive, NC Kenansville loamy sand Conventional fall and spring

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7 Materials and Methods Location Specifics cont. Harrisburg Planted with planter AG2031 soy DKC SSRIB corn R15 16 Rep 2 R13 14 Rep 2 R11 12 Rep 2 R9 10 Rep 2 R7 8 Rep 1 R5 6 Rep 1 R3 4 Rep 1 R1 2 Rep 1 Leland Planted with planter AG4632 soy DKC SSRIB corn R7 8 Rep 1 R5 6 Rep 1 R3 4 Rep 1 R1 2 Rep 1 Mt. Olive Planted by hand AG5605 soy DKC SSRIB corn R15 16 Rep 2 R13 14 Rep 2 R11 12 Rep 2 R9 10 Rep 2 R7 8 Rep 1 R5 6 Rep 1 R3 4 Rep 1 R1 2 Rep 1

8 Materials and Methods Application 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 spray volume, 40 psi, and 3.0 mph

9 Materials and Methods Ratings Soybean control = soybean death Stand counts emergence and control 28 days after treatment for PRE and POST Herbicide damage to corn if seen

10 Materials and Methods Herbicides PRE 1. TripleFlex - (acetochlor+flumetsulam+clopyralid) 2. Resolve Q - (rimsulfuron+thifensulfuron) 3. Atrazine 4F - (atrazine) POST 1. RoundUp Weathermax - (glyphosate) 2. Capreno - (thiencarbazone+tembotrione) 3. Liberty - (glufosinate) 4. Resolve Q - (rimsulfuron+thifensulfuron) 5. TripleFlex - (acetochlor+flumetsulam+clopyralid) 6. WideMatch - (clopyralid+fluroxypyr)

11 Materials and Methods Herbicides cont. PRE Herbicide Treatments Active Ingredient (AI) Product rate/acre AI/Acre (lbs) glyphosate (control) 22 oz 0.95 atrazine 2 pt 1.0 rimsulfuron+thifensulfuron acetochlor+flumetsulam+ clopyralid 1.25 oz (wt) 2 pt 2.88, , 0.03, Corn Timing After planting but prior to emerging Soybean Timing After planting but prior to emerging

12 Materials and Methods Herbicides cont. POST Herbicide Treatments Active Ingredient (AI) Product rate/acre AI/Acre (lbs) glyphosate (control) 22 oz , 3 oz thiencarbazone+tembotrione glufosinate 22 oz , 1.25 oz (wt) rimsulfuron+thifensulfuron , 2 pt 0.03, acetochlor+flumetsulam+clopyralid , 1.33 pt clopyralid+fluroxypyr Corn stage of development at application V4-V6 Soybean stage of development at application V3-V4

13 Results and Discussion 2 Harrisburg, SD Precipitation June and July Average = 7" Total = 4.9" Deviation = -2.1" Precipitation (inches) Planting PRE POST Final Count /1 6/11 6/21 7/1 7/11 7/21 7/31 Source:

14 Results and Discussion Leland, MS Precipitation June and July Average = 8.56" Total = 3.24" Deviation = Precipitation (inches) Planting PRE POST Final Count 0 6/1 6/11 6/21 7/1 7/11 7/21 7/31 8/10 Source:

15 Results and Discussion 3 Mount Olive, NC Precipitation May and June Average = 7.63" Total = Deviation = Precipitation (inches) Planting/ PRE POST Final Count 0 5/1 5/11 5/21 5/31 6/10 6/20 6/30 7/10 Source:

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18 Conclusion and Discussion PRE 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

19 Conclusion and Discussion PRE Herbicides Relatively low amount of atrazine used in study; control should increase with rate increase Herbicide carryover is a concern with atrazine and clopyralid products Soil texture, organic matter, ph, clay content and rainfall should be considered prior to herbicide application for rates and carryover potential

20 Conclusion and Discussion POST Herbicides Best control achieved with clopyralid + fluroxypyr across 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

21 Conclusion and Discussion POST 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

22 Conclusion and Discussion POST 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 glufosinatetolerant No carryover concerns

23 Conclusion and Discussion Herbicide 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

24 Conclusion and Discussion Herbicide 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

25 Questions?