Adjuvants and Herbicides Peanut Notes No. 66 2019

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In my experience traditional 80/20 surfactants and crop oil concentrate are adequate to optimize herbicide performance in our region of the United States. Certainly there are products that increase the rate at which an herbicide might perform but in general, ultimately weeds die when the appropriate 80/20 surfactant or crop oil concentrate is used. Under the very hot and dry conditions we currently have, use caution when using an adjuvant that heats things up with herbicides for weed control. This could, in some cases, increase injury on peanuts. In some cases growers are applying residual herbicides with contact herbicides and not adding surfactant. Some herbicides, Dual Magnum for example, likely have emulsifiers that might behave like a surfactant. Look closely at product labels and use an adjuvant if it is recommended. Don’t forget that with paraquat the recommendation is 1 pint of 80/20 surfactant per 100 gallons. For PPO inhibitors (Cobra, Ultra Blazer, and Storm) use 1 quart per 100 gallons. The PPO inhibitors can be applied with crop oil concentrate as well. See labels for specifics. Crop oil concentrate is generally applied at 1 to 2 pints per acre or 1.0% on a volume basis of spray solution.