Straight Talk About Dicamba: Explaining 2017, Preparing for 2018

Transcription

1 Straight Talk About Dicamba: Explaining 2017, Preparing for 2018 Thomas J. Peters Extension Sugarbeet Agronomist and Weed Control Specialist North Dakota State Univ. / Univ. of Minnesota

2 STATE RESTRICTIONS - MN 24(C) EXPIRES ON 10/1/2018 No application shall be made after June 20, 2018 No application shall be made if the air temperature of the field at the time of application is over 85 degrees Fahrenheit OR if the National Weather Service s forecasted high temperature for the nearest available location for the day exceeds 85 degrees Fahrenheit. Local National Weather Service forecasts are available at Retail sale to and use ONLY by Certified Applicators Registrants are responsible for dicamba-specific training ~90 minute, in-person session that is free of charge Attendance records maintained by registrants One training session satisfies requirements for any of the three dicamba products MCPR will maintain training session calendar at: Regents of the University of Minnesota. All rights reserved.

3 Dicamba Learning from 2017 Inversions were not understood; occur more frequently than realized Handling and mixing; a small amount of contamination will cause damage to sensitive soybean Dicamba herbicide is weed control tool and not a weed control program

4 Please ask questions throughout! Dicamba History 2017 in Review and Preparing for 2018 Weed Management Q & A 5 min 15 min 10 min 5 min

5 Dicamba Herbicide Synthetic auxin herbicide in the benzoic acid chemical family Discovered in 1958 and first marketed in 1964 as Banvel DMA salt Clarity DGA salt marketed in 1992 Sixth most widely used herbicide in the U.S., with more than 25 million acres of farmland treated annually Controls annual and perennial broadleaf weeds in grass crops Would offer a different mode of action for control of tough-to-control broadleaf weeds in soybean Slide credit: Dr. Jim Griffin, Louisiana State University

6 Vapor Pressure of various compounds Pressure at which vapor phase is in equilibrium with its liquid/solid forms Compound mmhg at 100F SI units Volatility Glyphosate Non-volatile Dicamba salt Non-volatile Dicamba acid at 75F 10-5? Dicamba acid at 100F 10-3? Eptam Volatile Water Volatile Acetone Volatile Ammonia Volatile Challenge: Can dicamba acid be formulated in salts that are non-volatile? Challenge: Are dicamba salt formulations durable?

7 Engenia Herbicide Most Flexible and Advanced Dicamba for DT Crops DGA Dicamba The Boat: Dicamba acid The Line: Ionic Bond The Anchor: DGA Salt The Anchor: BAPMA Salt BAPMA is a Bigger and Stronger Anchor for Dicamba Always read and follow label directions. Engenia is a US EPA Restricted Use Pesticide.

8 Mechanisms of Off-target Movement Thermogravimetric Analysis % Relative Volatility Banvel herbicide Clarity herbicide Engenia herbicide >90% Reduction in Volatility Compared to Clarity herbicide Test conditions: Temp = 100 C/212 F, Time = 20 hours, Air flow = 60 ml/min, RH = 0% Volatility has been addressed with new low volatility formulations and restrictions on tank mixtures and adjuvants Always read and follow label directions. Engenia is a US EPA Restricted Use Pesticide.

9 Estimates of impacted acres, by state State Date Complaints Investigation Estimated acres Minnesota August 25, ,000 North Dakota August 21, ,000 August 10, 2017 Total: ~3.6 million October 15, 2017 Slide Credit: Dr. Kevin Bradley, University of Missouri

10 Dicamba Damage Complaints in Different Counties of MN Total dicamba-related damage cases 249 Total counties reporting: 47 Misuse investigations assigned to Ag Chemical Investigator s 55 Normal year pesticide misuse investigations - ~100 Slide credit: Dr. Jeff Gunsolus, Univ of Minnesota

11 What happened in 2017? Cupping leaf phenotype appeared 14 to 21 days after application Areas with the most Xtend soybean and sprayed with Engenia, XtendiMax, or FeXapan are areas with the greatest amount of offtarget movement and damage Air temperature and lack of precipitation in late June and July exasperated damage in Cass County, ND Was volatility related to air temperature? Was volatility related to lack of precipitation? How?

12 Dicamba impact on North Dakota and Minnesota agriculture Soybean acreage in 2017 o o North Dakota, 7.2 million acres Minnesota, 8.2 million acres Time of application o o Small grains and corn, May and early June Soybean, June and early July Dicamba rate: o o o 0.5 to 1 fl oz ai, wheat 2 to 4 fl oz ai, corn 8 fl oz ai, in dicamba tolerant soybean Technology adoption and market share growth

13 Observed soybean injury (non DT) from RR Xtend Soybean Technology Image Credit: BASF Particle movement (including inversions) Volatilization Sprayer cleanout - contamination Misapplication

14 Lowest Observable Dose Causing Significant Visual Crop Response Source: Dr. Bob Hartzler, Iowa State University, Not all Drift is Created Equal Regents of the University of Minnesota. All rights reserved.

15 Soybean flat dose response to dicamba Soybean show leaf cupping at a wide dose rate Leaf cupping Stunting Chlorosis/necrosis Aborted flowers Distorted pods/seeds

16 Dicamba Flat Response Curve 8-Fold difference in exposure 1/1000X 1/500X 1/2000X 1/4000X Based on 0.5 lb ae/a as the 1X rate Can be difficult to differentiate symptomology across rates 2017 BASF field research trials These slides were prepared by BASF to satisfy US EPA requirements. Please check with your state pesticide regulatory authority as additional requirements may be imposed by state regulatory authorities. DATE 11/17.

17 There are four routes by which dicamba can move from its intended target Physical drift at the time of application Wind speeds are too great Use of improper nozzles that produce fine droplets Tank contamination via improper spray tank cleanout It takes very, very little dicamba in the tank to cause problems on non-xtend soybean that are sprayed after a dicamba application Small quantities of dicamba in the transfer equipment Temperature inversions Evening hours around sunset, persist for 8 to 10 hours When the air nearest the earth's surface becomes cooler than the air above it Volatility Dicamba is an inherently volatile herbicide We know that the older dicamba formulations are less durable; lower molecular weight, weaker ionic bond

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19 Wind speed requirements Spray when winds are 3 to 10 MPH Wind Speed Label Requirement Comments < 3 mph DO NOT spray Avoid temperature inversions 3 to 10 mph Spray ONLY IF wind is blowing away from neighboring sensitive crops This includes nondicamba tolerant soybeans > 10 mph DO NOT spray Consider wind gusts Monitor and document wind speed and direction before and after application. Measure wind speed at boom height in field

20 How much dicamba per acre does it take to injury sensitive soybean? Slide Credit: Stanley Culpepper, Univ of Georgia

21 Simple handling and mixing model Few points for possible contamination Sprayer is the only source of contamination concern Image credits: BASF

22 Complex handling and mixing model Multiple points for possible contamination Product mixing Nurse truck hot loads Product storage In-field mixing and filing Product transfer Anything formulated product or spray solution touches can be a source of contamination Image credits: BASF

23 Temperature inversions, impact on off-target movement Small droplets can remain suspended in air and move great distances for as long as inversion lasts Symptomology over larger geographical area Direction and distance of movement is not predictable DO NOT make applications when an inversion exists at the field level

24 Slide Credit: Daryl Ritchison

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26 Some things a grower can control Once the droplet leaves the nozzle then no control V1 11/2016

27 What happens to bapma salt or Vapor Grip after droplet is released from nozzle? 1. Deposit formation after water evaporation 2. Affect of pools of H+ on leaf surface and soil 3. What is the effect dew and small rain events

28 Dicamba is water soluble Herbicide H20 Solubility (ppm) Prowl 0.33 Atrazine 35 Callisto 160 Harness/Surpass 282 Dual Magnum 530 Glyphosate 10,500 Dicamba 250,00 Paraquat 620,000

29 Absorption of dicamba in plants Adsorption of dicamba to soil Soil adsorption coefficient amount of chemical adsorbed to soil per amount of water Kd = concentration of chemical in soil/water Kd values vary greatly because OM is not considered in the equation pie absorption into body Koc = (Kd * 100)/ % organic carbon Koc is also known as organic carbon-water partition co-efficient pie adsorbed onto body Kd or Koc measures the mobility of a substance in soil. A very high value means it is strongly adsorbed onto soil and organic matter and does not move in soil. A very low value means it is highly mobile in soil.

30 Dicamba physical properties Slide Credit: R Zollinger, NDSU Common Name Trade Name Koc (mg/l) Kd (mg/l) Acetamides Warrant DNAs Treflan 3,000 9,000 EPTC Eptam Sulfentrazone Spartan 43 1 Common Name Trade Name Koc (mg/l) Kd (mg/l) Glyphosate Roundup PowerMax 24, ,4-D 2, 4-D Clopyralid Stinger 60 Picloram Tordon Common Name Trade Name Koc (mg/l) Kd (mg/l) dicamba

31 Impact of AMS on Dicamba Volatility Dicamba Loss (%) BASF Lab Engenia Study Engenia Engenia herbicide: + AMS 12.8 fl oz/a AMS 0.5% w/v at 10 GPA + AMS Temperature (C) Temperature ( F) AMS increases potential volatility by 20 times Always read and follow label directions. Engenia is a US EPA Restricted Use Pesticide. Test Conditions: Duration: 24 hours Air flow: 0.5 l/min using 2.5 l tank RH: 35% Substrate: glass Engenia herbicide Solo These slides were prepared by BASF to satisfy US EPA requirements. Please check with your state pesticide regulatory authority as additional requirements may be imposed by state regulatory authorities. DATE 11/17.

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33 Dicamba is a tool and not a program Observed RR, LL, and Xtend soybean in 2017 Observed clean and dirty fields with each technology Herbicide trait will not solve weed resistance A solid weed management plan can

34 Weed emergence patterns Werle, Rodrigo. Lowell D. Sandell, Douglas D. Buhler, Robert G. Hartzler, and John L. Lindquist. Predicting Emergence of 23 Summer Annual Weed Species Weed Sci. 62:

35 Kochia control in LibertyLink and Xtend Soybean, Barney, ND Herbicide treatment 1 Dual Magnum + Valor / Liberty Sharpen + Warrant / Engenia + PowerMax Engenia / Engenia + Warrant / PowerMax Engenia + PowerMax/ Engenia + PowerMax Application PRE / POST PRE / POST PRE / EPOST / POST EPOST / POST Herbicide rate (oz, fl oz or pt/a) Jun 1 Jun 29 Sept pt + 1 fl oz / 29 fl oz 1 fl oz + 3 pt / 13 fl oz + 28 fl oz 26 fl oz / 13 fl oz + 3 pt / 32 fl oz 13 fl oz + 28 fl oz/ 13 fl oz + 28 fl oz % control LSD (0.05) Liberty applied with N-Pak ammonium sulfate at 3 lb/a, Engenia plus PowerMax with Class Act Ridion at 1% v/v, PowerMax with N-Pak ammonium sulfate at 1.5 lb/a and NIS at 0.25% v/v.

36 Lambsquarters control (early germinator) from preemergence and postemergence herbicides, near Moorhead, MN in 2017 Treatment 1 Rate oz/a* or fl oz/a Lambsquarters Timing Jul 27 Aug 23 % % PowerMax / PowerMax 28 / 28 EPOST / POST 98a 96a Rowel + XtendiMax / 2* + 22 / PRE / XtendiMax +PM POST 96a 83a Dual Magnum + Valor SX / 1.3 pt + 2* / PRE / Liberty 29 POST 78b 58b Liberty / Liberty 29 / 29 EPOST / POST 94a 73ab Authority MTZ / Liberty 15* / 29 PRE/POST 98a 94a 1 PowerMax + XtendiMax with Class Act Ridion at 2% v/v plus Intact at 0.5% v/v. PowerMax alone with Prefer 90 NIS at 0.25% v/v plus N-Pak AMS at 2.5% v/v. Liberty alone or in tank-mixes with N-Pak AMS at 5% v/v.

37 Waterhemp control (late germinator) from preemergence and postemergence herbicides, near Moorhead, MN in 2017 Treatment 1 Rate oz/a* or fl oz/a Waterhemp Timing Jul 27 Aug 23 % % PowerMax / PowerMax 28 / 28 EPOST / POST 13b 0c Rowel + XtendiMax / 2* + 22 / PRE / XtendiMax +PM POST 88a 66b Dual Magnum + Valor SX / 1.3 pt + 2* / PRE / Liberty 29 POST 88a 79b Liberty / Liberty 29 / 29 EPOST / POST 93a 70b Authority MTZ / Liberty 15* / 29 PRE/POST 98a 98a 1 PowerMax + XtendiMax with Class Act Ridion at 2% v/v plus Intact at 0.5% v/v. PowerMax alone with Prefer 90 NIS at 0.25% v/v plus N-Pak AMS at 2.5% v/v. Liberty alone or in tank-mixes with N-Pak AMS at 5% v/v.

38 Dicamba Recommendations for 2018 What is my most important weeds? o Do they emerge early or late? Target early postemergence application timing o PRE? No! There are much better PRE heribicides o Target early POST

39 Thank you for your Support Tom Peters Extension Sugarbeet Agronomist and Weed Control Specialist (office) (mobile)