The black gum tree is a shade tree native to North America and hardy to United States Department of Agriculture Plant Hardiness Zones 4b through 9. Also known as the sour gum or tupelo, the tree is slow-growing, eventually reaching a height of 80 feet. The dark gray bark is smooth when immature, becoming cracked as the tree ages. The leaves are elliptical ovals and green during the growing season. In the fall, the leaves turn yellow, orange, red and burgundy. The black gum is susceptible to fungal diseases including botryosphaeria canker, leaf spot infections and heart rot infections.
Botryosphaeria canker is caused by the fungus of the same name, according to the Virginia Tech Cooperative Extension. The fungus attacks trees that are stressed, so prevention is key to keeping black gum trees healthy. The symptoms include branch wilt and dieback. In extreme cases, the bark peels away, revealing discolored underbark. Cankers that look like wounds may appear on branches. These wounds ooze gum from the interior of the tree. The fungi attack trees through pruning wounds, cracks in the bark or naturally occurring pores in the leaves. There is no treatment. Prevent the disease by providing adequate fertilizer and water; plant only healthy black gum trees. Remove and destroy any dead branches.
Black Leaf Spot
Black leaf spot is one of several leaf spot diseases caused by fungus. These leaf spot diseases affect all shade trees, including the black gum tree, according to the University of Illinois Extension. The symptoms include raised, black spots with ragged edges on leaves. Leaf spots multiply at the end of the growing season. In severe cases, the leaves change color, wither and can drop prematurely from the tree. The disease is mostly cosmetic, although if black leaf spot appears in consecutive years, trees can become weakened, making them vulnerable to other diseases and pest infestation. Prevent the disease by practicing good habits such as regular watering and fertilizing the tree to keep it healthy.
Black gum trees are susceptible to heart rot fungal disease in which the heartwood and limbs decay from the inside out. There are several fungi that cause this disease, according to the University of California. Oak root fungus causes a white rot that appears between the bark and the underbark. This fungus enters the black gum tree through the root system. Artist's conk is a fungus that enters the tree through wounds or openings in the bark. Rings, or conks, form on the bark near the ground. Varnish fungus rot is a slow moving white fungus that attacks the roots and trunk of black gum trees.
Prevent heart rot disease by keeping black gum trees healthy through regular fertilizing and watering. Use proper pruning techniques, such as pruning outside the ridge of the branch bark and .leaving a collar of wood that can heal.
- Virginia Tech Cooperative Extension: Botryosphaeria Canker and Dieback of Trees and Shrubs in the Landscape
- University of Illinois Extension: Fungal Leaf Spot Diseases of Shade and Ornamental Trees in the Midwest
- University of California: Statewide Integrated Pest Management Program: Wood Decay Fungi in Landscape Trees
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