Insects and Diseases of Trees in the South

by Anonymous

VERTICILLIUM WILT

Verticillium wilt, caused by common soil-inhabiting fungi belonging to the genus Verticillium, is found on a number of hardwood hosts. In southern and eastern United States elms and maples are attacked throughout their natural ranges.

Wilting foliage and defoliation of elms caused by Verticillium wilt.

Infected trees may die within a few weeks after the first symptoms are observed, or they may survive for years. The first symptoms of the disease involve a wilting of the foliage, with the leaves turning yellow and finally brown. The early symptoms are often restricted to a single limb or portion of the crown. Vascular discoloration, which is brown in elms and green in maples, is present in the outer sapwood. In elms, this discoloration is similar to that produced in trees having Dutch elm disease.

This disease is not of serious consequence in forest stands. However, it is often extremely important in high value shade trees. Dead or dying limbs on lawn trees may be pruned out. This may not always save the tree, but may help keep it alive for years. Trees should be well watered and fertilized as necessary. If a lawn tree dies from Verticillium wilt, it should be replaced by a resistant species.