Many growers will begin their fungicide sprays for leafspot disease the week of June 29. We have a lot of options, but starting with chlorothalonil has been an effective approach for a long time. LeAnn will have the leafspot advisory available in July. This is an effective tool in helping you decide when to apply fungicides (or not) based on weather conditions (temperature and humidity.) We will provide more information as we move into this phase of the crop cycle.

We do have some cases where fungicides can decrease efficacy of herbicides. I’ll provide more information on this in a second post on this. We have documented less grass control when clethodim is mixed with chlorothalonil. We need to include crop oil concentrate with clethodim, and the crop oil can speckle peanut leaves when mixed with chlorothalonil. It’s not the end of the world, but it can happen. Use the 16 oz/acre rate of clethodim if you mix chlorothalonil with clethodim plus crop oil concentrate to minimize any antagonism of grass control that might occur.