Powdery Mildew Appears

What’s that white stuff on my…. you name it….zinnias, lilac, pumpkin, dogwood. It’s powdery mildew, a common fungal disease that appears in late summer every year. Yes, it is a disease but there is no need for alarm. In most cases, it’s just cosmetic.
Actually, there are many different, related fungi that cause symptoms that we call powdery mildew. While related, in most cases they are specific to their host plants. For instance the powdery mildew on apple is not that same as the organism that affects lilac.

Commercial growers of pumpkin, apples, peaches and some other crops must manage powdery mildew or serious crop damage can occur. In backyard gardens, we can usually accept this damage caused by the disease. All deciduous plant leaves are due to drop in the next month so, powdery mildew or not their days are numbered.
Bottom line, don’t worry about powdery mildew. For a more complete story on this common disease see what Cornell University has to say.

Don’t worry about putting mildew infected leaves into the compost. Next year’s infections will come from many sources and the fungus will probably have trouble surviving the compost pile environment anyway.