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.
[Illustration: 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.