Michigan State University Extension
Ornamental Plants plus Version 2.0 - 00001227
01/01/98
Anthracnose may be a serious problem in wet weather. Infected leaves have dead areas following the midrib or larger veins. These light brown blotches may run together and, in severe cases, cause leaf drop. Trees of low vigor, repeatedly defoliated, may die. Trees defoliated several years in a row may need spraying. Apply the first spray at bud break and make additional sprays at 10 day intervals if average temperatures are below 55 degrees.
Canker diseases can either attack the trunk or the branches. Keep trees healthy by regular fertilization. Prune out diseased or dead branches.
Leaf blister symptoms are round raised areas on the upper leaf surfaces causing depressions of the same shape and size on lower leaf surfaces. Infected areas are yellowish-white to yellowish-brown. The disease is most serious in wet seasons.
A large number of fungi cause leaf spots but are usually not serious. Rake up and dispose of infected leaves. Chemical controls are usually not warranted.
Powdery mildew coats leaves with white powdery growth. Spraying may not be needed.
Oak wilt is a fatal disease beginning with a slight crinkling and paling of the leaves. This is followed by leaf wilting and browning of leaf margins then working inward. The symptoms move down branches toward the center of the tree. Cut down and destroy infected trees. The disease may be spread by insects or pruning tools.
Shoestring root rot attacks the roots and once inside moves upward, killing the cambium. The leaves are small, pale or yellowed and fall early. There is no practical control. Healthy trees may be less likely to be infected than trees of low vigor.
Chlorosis due to iron deficiency occurs on high pH soil. Sulfur will increase soil acidity. Trunk implants of plastic capsules containing a soluble iron source may overcome deficiency symptoms until the soil conditions are corrected.