Yellow Birch Canker and Shoot Blight |
| 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. |
Canker and shoot blight of yellow birch may be caused by either Diaporthe alleghaniensis or Gnomonia setecea. Yellow birch is susceptible to these fungi until the trees are about 3 inches in diameter.
From spring to early summer, both fungi cause black, sometimes sunken cankers in the outer bark. Later the fungus spreads to the inner bark and may discolor nearby wood. New shoots are infected and killed early in the growing season, sometimes forming "shepherd's crooks." Because it takes longer for a canker to girdle the older, woody stems, these stems die later in the year. The leaves beyond the canker wilt, and the dead leaves remain attached to the tree for several months. Fruiting bodies form within the dead stem bark and burst out.
Leaf spots are caused only by Gnomonia setacea. They may appear at any time during the growing season, but most often the latter half. The brown spots usually are surrounded by yellowish zones. Small, black fruiting bodies develop within the leaf spots and dead stem bark.
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