Compatibility of Pesticides Peanut Notes No. 112 2020
There are a lot of questions about compatibility of herbicides and fungicides. Take a look at chapter 9, page 165 in 2020 Peanut Information for comments on compatibility. It has been a number of years since we have conducted intensive research on product compatibility. There are so many possible combinations we have not had the resources to address all of the possibilities. In general, we don’t see issues with broadleaf weed control when we apply mixtures of herbicides and fungicides. We do see less grass control with clethodim when we apply it with chlorothalonil and some of the other fungicides. We recommend that the highest rate of clethodim be applied to overcome the antagonism. In limited research we did not see a negative impact of herbicides on fungicide performance. Keep in mind that we apply 4 to 6 fungicide sprays for leaf spot and stem rot, so there is a lot of compensation for a minor difference in efficacy for a single fungicide spray in a comprehensive program. We have not observed issues when insecticides are applied in combination with other pesticides.
One of the most important things to do is make sure the mixture does not settle in the tank. This is particularly important when you consider products that contain manganese and 2,4-DB. Be very careful in general with physical compatibility, but specifically with manganese. We can often live with a little less control and possibly a little more injury. BUT it is painful to address settling in the tank.