Is there something I can add to the soil to prevent the powdery mildew from attacking my vegetables? I have been unable to grow zucchini for the past few years because all of the plants have been stricken with the white chalky coating...killing them off.
Powdery Mildew on Zucchini Plants
Certified GKH Gardening Expert
Powdery mildew is not soil borne so treating your soil will not prevent powdery mildew. Powdery mildew needs living plant tissue to grow on. The best treatment for powdery mildew is stay proactive by working to prevent the conditions on your plants that foster powdery mildew.
The following articles will discuss what these conditions and what corrective actions to take: