The maple tree family consists of more than 120 species of deciduous trees and shrubs. Many variations of the maple family can reach mature heights of up to 120 feet, and most produce colorful foliage from spring through early winter. These showy trees have moderate growth rates. These trees are fairly disease-resistant but are susceptible to several trunk diseases that can cause permanent injury and even death to the tree.
Phomopsis gall is a fungal disease that is common amongst the maple tree family. Though there is little known about the lifecycle of this fungal disease, it is clear that the disease is not fatal to the maple tree. Infected maple trees generally show symptoms in the fall as the leaves begin to drop. The infected trunk and branches will display round wooden galls. The galls are initially smooth but harden and crack with age. As the infection progresses, the trunk and branches become girdled with the infected galls. There is no fungicidal treatment for this disease. Prune away infected areas when possible.
Wetwood is a bacterial disease that infects the central core and bark of the maple tree. This disease is caused by several variations of bacteria that penetrate the tree through the root system. The symptoms of wetwood are limited to the lower areas of the trunk. Infected maple trees will first display a yellowish-brown discoloration near the tree’s central core. The progression of the disease causes an increase of internal gas pressure. This increased pressure results in the exudation of bacterial slime that is accompanied by a foul smell. Maple trees that are infected with wetwood will also experience splitting and cracking of the trunk, premature defoliation and dieback. There are no bacterial treatments for this disease. Greatly reduce the potential for infection with regularly watering and fertilization.
Heart rot is a fungal disease that usually appears after long periods of rain. The fungus of this disease cannot penetrate the healthy wood of a maple tree. Instead, this disease attacks the tree through its open wounds. Depending on the variation of heart rot, the infected maple tree will develop either a soft, spongy wood that crumbles to the touch or a brown decay of wood that falls apart in chunks. Many maple trees will develop fungal sprouts and mushrooms on and near the trunk and throughout the tree. Heart rot cannot be cured with fungicidal treatments. However, the potential for heart rot is greatly reduced when the tree’s wounds are kept to a minimum. Avoid using mowers and power equipment near the tree.