Aspen shoot 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.
Aspen shoot blight is caused by Venturia populina on balsam poplar and the closely related Venturia tremulae on quaking and bigtooth aspen. These fungi, which occur throughout the range of balsam poplar, quaking aspen, and bigtooth aspen, cause leaf spots and kill the shoots.
The symptoms produced by both fungi are similar. Angular leaf spots form in early summer and enlarge until the entire leaf is blackened and wilted. The fungus spreads down the stem if the leaf (particularly on quaking aspen) and blackens the shoot. The shoot then withers and forms a characteristic "shepherd's crook." Under moist conditions, dark-greenish spores form on the infected leaves and shoots.
Severe outbreaks of this blight rarely occur in successive years, and the fungus invades and kills only the current year's tissue. The repeated loss of current growth can cause stag-headed trees and delay tree harvest, but trees older than 5 years are seldom affected. Therefore, the disease is of little economic importance in natural stands.
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 Photo by Jane Taylor, USDA Forest Service, Bugwood.org |
