Problem Identifier Unit Screen//v.w/ RR Template

Problem Identifier Unit Screen//v.w/ RR Template Verticillium Wilt

Problem
The leaves on a branch turn yellow at the margins, then brown and dry. During hot weather, the leaves may wilt. New leaves may be stunted and yellowish. The infected tree may die slowly, branch by branch, over several seasons. Or the whole tree may wilt and die within a few months. Some trees may recover. The tissue under the bark on the dying side shows dark streaks, which may be very apparent or barely visible when exposed. To examine for streaks, peel back the bark at the bottom of the dying branch.

Analysis
This wilt disease affects many ornamental trees and shrubs. It is caused by a soil-inhabiting fungus (Verticillium species) that persists indefinitely on plant debris or in the soil. The disease is spread by contaminated seeds, plants, soil, equipment, and ground water. The fungus enters the tree through the roots and spreads up into the branches through the water-conducting vessels in the trunk. The vessels become discolored and plugged. This plugging cuts off the flow of water and nutrients to the branches, causing the leaf discoloration and wilting. For more information about verticillium wilt, see Verticillium or Fusarium Wilt.

Solution
No chemical control is available. Fertilize and water the affected tree to stimulate vigorous growth. Remove all dead wood. Do not remove branches on which leaves have recently wilted. These branches may produce new leaves in 3 to 4 weeks or next spring. Remove dead trees. If replanting in the same area, plant trees and shrubs that are resistant to verticillium. For a list of resistant trees and shrubs, see Plants Resistant to Verticillium Wilt.

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