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Understanding Herbicide Additives

Dr. Eric P. Prostko
Extension Weed Specialist
University of Georgia
Tifton, GA

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TABLE OF CONTENTS

Understanding Herbicide Additives Herbicide Additives: When do you need them?? Herbicide Additives: A balancing act Herbicide Additives: What do they do?? Herbicide Additives: Types Herbicide Additives: Non-Ionic Surfactants (NIS) Herbicide Additives: How surfactants work Herbicide Additives: Organosilicone Surfactants Herbicide Additives: Crop Oil Concentrates (COC) Herbicide Additives: Fertilizers Herbicide Additives: Buffers Is the pH of spray water really important? Rate of Herbicide Degradation in Water at pH of 5, 7, and 9 Herbicide Additives: Compatibility Agents Herbicide Additives: Drift Control Agents Drift Fallout As Influenced By Pressure and Nalcotrol Herbicide Additives: Stickers Herbicide Additives: How much do they cost?? Herbicide Additives: Do they work??? The influence of additives on Classic (0.5 oz/A) performance in soybeans - 21 DAT Commercial surfactant effects on the performance of Roundup/Honcho Influence of additives on sicklepod control with Cadre - 68 DAT Herbicide Additives: Final Thoughts

SLIDE CONTENTS

Understanding HerbicideAdditives Dr. Eric P. Prostko Extension Weed Specialist University of Georgia Tifton Herbicide AdditivesWhen do you need them?? postemergence applications certain weeds stressful conditions cheap insurance? may increase crop injury PPT Slide Crop Injury Enhanced Performance Herbicide Additives A Balancing Act Herbicide AdditivesWhat do they do?? modify or maximize performance increase absorption and retention * decrease surface tension of water * prevent interaction with Ca, Na * increase permeability of cell membrane and cuticle Herbicide AdditivesTypes non-ionic surfactants (NIS) organosilicone surfactants crop oil concentrates (COC) fertilizers (N) buffers compatibility agents drift reduction agents stickers Herbicide AdditivesNon-Ionic Surfactants (NIS) aliphatic alcohols + siloxane + fatty acids decrease surface tension of water need at least 80% active ingredient 0.25% v/v Activator 90, X-77, Latron AG-98, Induce PPT Slide How Surfactants Work Herbicide AdditivesOrganosilicone Surfactants silicone based 0.025 - 0.25% v/v Silwet L-77, Kinetic Herbicide AdditivesCrop Oil Concentrates (COC) petroleum or vegetable oil based 83-85% oil + 15-17% NIS 1% v/v help move herbicide across cuticle reduce surface tension of water reduce drying time Agri-Dex, Peptoil (petroleum) Sun-It, Prime Oil II (vegetable) Herbicide AdditivesFertilizers 32% UAN (1 qt/A) ammonium sulfate (17 lbs/100 gallons) used with COC or NIS increase leaf burn increase membrane permeability prevent interaction with Ca, Mg, and Na Herbicide AdditivesBuffers maintain or reduce pH prevent alkaline hydrolysis (> 7 pH) Buffer P.S, Penetrator Plus Is the pH of spray water really important? may affect some insecticides has not affected the performance of herbicides in most studies length of time in tank is relatively short Rate of Herbicide Degradation in Water at pH of 5, 7, and 9 C. Boerboom. 1995. University of Wisconsin Water pH Herbicide AdditivesCompatibility Agents maintain emulsion stability/liquid fertilizer 0.12-0.50% v/v depending upon fertilizer Blendex, Merge, Unite, Herbicide AdditivesDrift Control Agents “thickeners” increase droplet size of pesticide/water mixes $0.10-$1.00/A 38F, Anchor, Array, Border, Chem-Trol, Corsair, Direct, Drifgon, Driftgard, Drop Zone, Get Down, Lo-Drift, More, Nalcotrol, Submerge, Sta-Put, Windfall Drift Fallout As Influenced By Pressure and Nalcotrol Source: W. Bowers. 1975. Ohio State Univ. Extension, Facts #1203. Herbicide AdditivesStickers “adhesives” maintain protective sprays fungicides, insecticides contain latex or casein AAdhere, Bond, Surfix Herbicide AdditivesHow much do they cost?? Chart based upon 20 GPA sprayer output Herbicide AdditivesDo they work??? The influence of additives on Classic (0.5 oz/A) performance in soybeans - 21 DAT Source: Fielding and Stoller. 1990. Weed Tech. 4:264-271. S = X-77 @ 0.25% v/v N = 28% UAN @ 1 gal/A Commercial surfactant effects on the performance of Roundup/Honcho Source: North Dakota State University, 1993-95 Influence of additives on sicklepod control with Cadre - 68 DAT A. S. Culpepper, 1999 LSD 0.05 = 5 Applied to 4-8” CASOB Herbicide AdditivesFinal Thoughts read label COC > NIS avoid “miracle” products