Chestnut Blight
From Bugwoodwiki
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USDA Forest Service. 1979. A guide to common insects and diseases of forest trees in the northeastern United States. Northeast. Area State Priv. For., For. Insect and Disease Management., Broomall, PA. p. 123, illus.
Chestnut blight, caused by the introduced fungus Endothia parasitica, was first reported in the United States in 1904. Within 50 years, it has spread through the entire range of American chestnut, killing nearly all of the trees. The fungus also attacks European chestnut and post oak, and causes slight injury to maple, hickory, and sumac trees. Many attempts have been made to develop a variety of American chestnut resistant to blight, but none has been successful.
The fungus enters through wounds and produces cankers on branches and stems. Branch cankers kill the branches, causing the leaves to turn yellow and wilt. Stem cankers girdle and kill the entire tree. Sprouts often grow from the stumps of killed trees. These sprouts also become infected and eventually die.
Cankers on young trees and branches are yellow-brown. Fruiting bodies develop on the bark at the canker. On older trees, the thicker bark splits up and down, and fruiting bodies develop in the cracks. Asexual fruiting bodies (pycnidia) develop, appearing as minute, orange blisters. They release spore masses in wet weather forming curled, yellow-orange tendrils called "spore horns." These sticky spores are dispersed by rain, insects, birds, and other animals. Sexual fruiting bodies (perithecia) are tiny flask-shaped pustules that produce ascospores. The ascospores are wind-dispersed.
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 Photo by John H. Ghent, USDA Forest Service, Bugwood.org |
