Verticillium Wilt |
| 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. |
Verticillum wilt, caused by the fungus Verticillium albo-atrum, affects many genera of trees and shrubs, especially maple. Foliage of affected trees may wilt at any time during the growing season. Sometimes only a few branches wilt, sometimes a whole section of crown, and sometimes the entire crown. If all branches are affected, the tree dies rapidly. Some trees that show a small amount of wilt may recover and not show wilt in following years. Drought or insect attacks increase wilting and hasten death of infected trees.
The Verticillium wilt fungus is soil-borne and can persist many years in soil without host plants. The fungus infects trees through root and stem wounds and may be carried from infected to healthy trees on pruning tools. The fungus fruits and spreads throughout the tree in the water-conducting vessels of the sapwood. The vessels become discolored after the fungus reaches them, as does the springwood of the current year's growth. In stem cross sections, discoloration is seen as spots or as partial-to-complete rings involving one or more annual growth rings. In wilting trees the discolored streaks in the sapwood may be limited to the trunk, extend only a few inches into the basal portion of wilting branches, or extend to the tips of wilting branches.
Symptoms; crown with wilt symptoms
USDA Forest Service - Missoula Archives, USDA Forest Service |
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