Verticillium wilt is caused by a fungus that is found in the soil in the tree's root zone. This is a very damaging fungus for which there is no chemical control. The fungus is spread by lawn equipment, ground water, soil transfer, and contaminated seeds; and may affect trees, shrubs and ornamentals.
The fungus enters the tree through the roots and is carried up the tree through the water conducting cells. As the fungus migrates to the branches the conduit cells become plugged with fungal growth, interrupting the flow of water and nutrients to the leaves and other living tissue.
Leaves on a branch will wilt as the branch dies. Peeling the bark at the base of a tree infected with verticillium wilt will reveal sapwood that has streaks of discoloration, signifying the presence of fungal growth. Although some trees may survive verticillium wilt, most will die, branch by branch over several growing seasons. Some trees may exhibit faster decline, dying in a matter of months.
Strict feeding and watering will afford the best chance of survival for an infected tree. All dead wood should be removed, but branches with recently wilted leaves should be allowed the opportunity to refoliate before being removed. Dead, or rapidly declining trees should be removed.
Only wilt-resistant specimens should be planted in an area which is known to harbor verticillium wilt. Some resistant trees which do well in the Houston area include , Oleander, Birch, Pear, Pecan, and Pine.