The post oak (Quercus stellata) is found growing along sandy or rocky ridges and in dry woodlands throughout the Southeastern and South Central United States. The slow-growing post oak tree normally reaches heights between 40 and 50 feet and is considered an ideal shade tree for parks and back yards. Although a relatively healthy breed, the post oak is susceptible to the same type of diseases that are commonly found in other oak trees.
The fungus anthracnose (Apiognomonia quercinia) affects the leaves and twigs of the post oak. Tiny brown spots appear on leaves located on the lower portion of the tree during the damp months of spring. Leaves will wither and defoliation of the tree is possible. The fungus will cause cankers to appear on new twigs which leads to twig die back. Sources at the University of Minnesota say that the best defense against anthracnose is to keep trees healthy, prune and destroy diseased branches and rake up dead leaves and burn them. Fungicides are successful in treating anthracnose and work best when applied at the beginning of bud break. Carefully follow all of the manufacturers instructions when using chemical treatments.
The post oak is susceptible to chestnut blight fungus (cryphonectria parasitica). Chestnut blight fungus is the cause of the near elimination of the American chestnut tree from eastern hardwood forests. Post oak trees that suffer from chestnut blight will have cankers that cause the bark to peel and often experience excessive die back. According to the U.S. Forest Service, there is no cure or effective treatment for chestnut blight fungus. Blight resistant and blight-free species of the post oak are recommended to ensure that your trees will not become infected with chestnut blight fungus.
The fungal pathogen Ceratocystis fagacearum is the cause of oak wilt. Symptoms of oak wilt include withering leaves in the upper parts of the tree; branches or parts of the tree crown turning a shade of reddish brown; and leaves turning yellow or brown and eventually falling from the tree. Preventative measures work best when attempting to control oak wilt. Don't prune trees between April 15 and July 1; any fresh wounds will attract beetles that may spread the disease to other trees. Dress all wounds with a layer of latex paint. According to Ohio State University, the only fungicide effective in suppressing oak wilt is one that contains propiconazole. The chemical propiconazole is injected directly into the root flare and should be done by a tree service professional. The disease is not curable but spreading is slowed by using propiconazole.
Oak Leaf Blister
The disease leaf blister is caused by the fungus Taphrina caerulescens. Most oaks are affected by leaf blister, including the post oak. Leaf blister is considered more of a cosmetic issue, although if the tree suffers severe cases over several seasons, the overall health of the post oak will be compromised. Light green or yellow blisters appear on leaves in the late spring and early summer months. As the blisters age they turn gray and take on a fuzzy appearance. Numerous blisters may join together, which leads to leaf distortion. Chemical control is usually not recommended for homeowners, but if constant attacks of leaf blister occur, the University of Arkansas Division of Agriculture states that fungicides containing chlorothalonil or mancozeb will effectively control the disease. Always follow the manufacturers instructions when using chemicals.