What to do about powdery mildew?

Every spring, we get a number of calls regarding discolored and unhealthy leaves on trees. We covered Anthracnose in an earlier article, which is a common fungal issue with trees.

Lately, I’ve seen an uptick in another fungal infection- Powdery mildew.

Powdery mildew is a very common infection amongst trees and shrubs in the Richmond area, with Dogwoods seeming to be the most frequent hosts. It’s distinctive white, dusty film can often be seen on the leaves of trees that spend most of their time in the shade or with limited airflow. Sometimes this is about the extent of what an infection will do, but frequently it is followed by curled, stunted, and scorched-looking leaves. Lately, I’ve seen quite a few Dogwoods (especially in the city) with brown curled leaves lower in the canopy while the upper portion (where airflow and sun hit the tree) looks fine.

While powdery mildew can make your tree look pretty terrible unless there are other stressing factors the infection is not lethal. More often than not the disease is considered “cosmetic”. 

There are a few very easy ways to help manage an infection. The first is to dispose of any affected leaf debris that’s fallen to the ground, in order to keep the fungal spores from continuing into the next season. Pruning overstory trees for better light and airflow penetration can also be a big help. If you’re thinking about planting a new tree but have concerns about powdery mildew, there are quite a few resistant varieties of trees nowadays. In very severe cases, treating your tree with a fungicide might be necessary.