Blight of chestnut has virtually eliminated the American chestnut from the landscape. The disease caused cankers on the branches then moved into the trunk killing the tree. There is no chemical control for the disease. Most chestnuts now grown are asiatic types and resistant to the disease caused by the fungus Endothia parasitica.
Twig canker is a problem on asiatic chestnuts. The symptoms are a brown discoloration on a twig. The disease girdles the twig and moves down to a larger branch. The leaves on the girdled branch wilt, turn brown and die. The canker is obvious due to callus formation at the canker margin. The disease attacks seedlings, very old trees, or unhealthy trees of any age. No chemical control is available. Prune out diseased branches and prevent the disease by keeping trees healthy.
Leaf spots caused by various fungi can be a problem. These are not serious so no chemical controls are listed. Clean up and dispose of diseased leaves.
Powdery mildew causes a white powdery growth on the leaves. Sprays of benomyl used according to label directions should take care of the problem.