Scleroderris canker
From Bugwoodwiki
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.
Scleroderris canker, caused by Germmeniella abietina (formerly Scleroderris lagerbergii), is a serious disease of conifers. Hard pines are most susceptible; red, jack and Scots pines are the species most commonly attacked. White pine and spruce are resistant, but may be attacked; balsam fir is immune. In the Lake States, the canker kills seedlings, small saplings, and the lower branches of larger pines. In New Hampshire, New York, and Vermont, where a more aggressive strain of the fungus is found, pines of all sizes are killed. The most severe damage occurs in depressions called "frost pockets," which may serve as reservoirs for large numbers of spores that infect trees in surrounding areas.
Because the fungus first attacks the buds and the progresses into the expanding shoots and needles, injury is most noticeable at the tips of branches. An early spring symptom is an orange discoloration at the base of the needles, a result of infection that occurred the previous summer. The needles then turn entirely orange and eventually brown. The dead needles drop readily, and bare dead shoots pointing skyward are a characteristic symptom. The fungus grows down the stem of the branch until it reaches the main stem, unless it is stopped when the branch dies. Main stems up to about 3 inches in diameter can be girdled or cankered. The tree also can be killed by the loss of foliage -- this is the way the more aggressive or "European" strain of Scleroderris most often kills trees. Small branch cankers, which are usually callused over, are common when the disease is caused by the European strain.
The most reliable symptom of Scleroderris canker is a green to yellow-green staining of the inner bark and wood beneath the bark of infected stems. The color is sometimes dull or even lacking, but among several infected branches there usually is one with a bright stain that resembles green ink.
G. abietina may produce both sexual and asexual spores. The fruiting bodies of both stages are very small, barely visible to the unaided eye. Fruiting bodies of the asexual stage are found most easily at the bases of the discolored (orange) or dead needles. Asexual fruiting bodies also form on bark. Spores of the asexual stage are spread by rain, usually infecting more branches of the tree on which they originated. The brown fruiting bodies of the sexual stage, when they form, appear on dead stems and needles. No sexual stage of the European strain has been found. The sproes are released during wet weather. Sexual spores are dispersed by wind and can spread the disease considerable distances. Sexual spore production and infection take place in July or August, and symptoms appear the following spring.
