Common Tree Diseases

There are many different diseases that can impact trees, and most are specific to a particular species of tree. Anthracnose is a disease that goes after hardwood trees, particularly American sycamores, white oaks, dogwoods and black walnuts. Anthracnose is widespread in the eastern part of the United States, where there is a high concentration of these families of trees. Common symptoms include discolored blotches or dead areas on the leaves, also known as leaf blight. Anthracnose is caused by several types of fungi that reproduce by means of spores. Spores are microscopic particles that spread through the air, especially during windy and rainy periods. They need wet weather to germinate, so anthracnose may become severe during years with long rainy periods. If a tree gets severely infected, it may lose its leaves, which is called defoliation. A round of anthracnose won't kill a tree, but repeated defoliation can weaken the tree and make it susceptible to other diseases. Its biggest impact is the reduction of shade trees in urban environments.

Root decay, or root rot, is another common cause of disease or death in trees. Roots secure the tree to the ground. They also supply nutrients and water, and the older the tree is, the larger the root structure. Trees with root problems can get blown over in wind or even fall over without warning under the weight of its leaves. It's hard to tell if your tree has root decay. There are two indicators to help determine if your tree has root decay: if the roots are broken or there is evidence of fungus.

Another devastating tree disease is the chestnut blight fungus, which has nearly wiped out the American chestnut from eastern forests. These fungus spores are spread during wind and rain and infect fresh wounds in the bark, creating a canker. The fungus pops up during moist weather and resembles an orange curled horn. To date, no cure has been found, but research is being done to develop a disease-resistant chestnut tree.