Order of Applying Fungicide, Chlorpyrifos, and Gypsum Peanut Notes No. 144 2020
Some farmers have gotten behind on applying both gypsum and chlorpyrifos. If I needed to apply these essentially on the same day, especially when a fungicide needs to be applied, I would apply the fungicide first and let it dry on the leaf surface, then apply chlorpyrifos and finally gypsum. I don’t know that there is any issue with order of these, but this seems to be the order that would decrease the likelihood of an issue. I do think that applying a pesticide (fungicide, insecticide, or herbicide) in a water spray solution immediately after gypsum has some risk of the pesticide not being absorbed into foliage, but I have no data to support this.