Q. Our city street in Pennsylvania is lined on both sides with Horse Chestnut trees. These trees were beautiful in the spring, but through the summer months many of the leaves turned yellow and brown, and dropped off long before they would usually drop in the fall of the year. What do you think is wrong with our Horse Chestnut trees and can we save them?
A. Horse chestnut (Aesculus hippocastanum) trees are susceptible to a fungal disease called leaf blotch. This fungal disease causes reddish-brown spots on the leaves that are often surrounded by yellow halos. Infected leaves turn brown and fall prematurely.
Leaf blotch is more severe when we have wet spring weather, but it can be equally severe during hot, dry weather.
Highly valued trees can be sprayed preventatively with cozeb (Dithane, Protect Turf and Ornamental Fungicide) fungicide, but treatment is not usually warranted. Although it is unsightly and messy, leaf blotch is not life threatening.