
Powdery mildew treatment on grapes ineffective
This is our second summer in this house with this established table grape vine. Last year, it was taken over by powdery mildew and all the grapes became mummified. This year, I started spraying them with sulfur (dusting sulfur added to water) according to the UC IPM guidelines in Spring. I also added a wire trellis so the vines could get more airflow and not hang on the ground.
These grapes looked fine within the last week and now they are almost all brown. ☹️ Some leaves looked infected and I have been pulling them off, but most look fine. Some of the vines had brown spots (which you can see some in the picture), but many of the vines looked healthy and green. The white spots you can see in this picture are from the residual sulfur. I’m not sure what I should have done differently.
Any recommendations on how to handle this next year? Could this be caused by something besides powdery mildew?