Garden Corner – Dieback in Landscape Trees – Could it be Verticillium Wilt?

Kelly Jackson
Christian County Extension Office

Dieback in Landscape Trees – Could it be Verticillium Wilt?

The stress of hot, dry conditions in midsummer can prompt leaf scorch in many landscape trees. However, extensive canopy dieback or tree collapse, particularly on one side of a tree, may indicate Verticillium wilt disease.

Verticillium wilt can affect a wide range of ornamental trees and shrubs, resulting in branch dieback, decline, and eventual tree death. Over 400 herbaceous and woody plant species have been reported as hosts for this disease. Some common hosts include lilac, maple, catalpa, magnolia, redbud, smoketree, and tulip poplar.

Symptoms include dieback and decline of branches scattered over the entire plant; or affected branches may be confined to one side. Leaves may be undersized, wilt suddenly, or exhibit marginal scorch, yellowing or browning. If bark of a limb is removed, a cut into the sapwood may reveal olive-green, brown, or black streaking in the water-conducting tissues of the plant, depending on the plant species.

As there is no cure for Verticillium wilt, ultimately, plant death occurs, particularly following drought stress. However, proper plant care may prolong the life of infected trees with mild symptoms.  Some basic plant care steps to follow include pruning and destroying symptomatic plant material. Be sure to sanitize tools between cuts. Water trees liberally as needed, especially during hot summer months, but avoid overwatering.

Because the fungus can survive in the soil for many years, remove and destroy severely infected plants. Avoid moving soil from the infested area to other parts of the landscape. Replant with resistant plant species or cultivars such as apple, beech, birch, dogwood, gingko, hawthorn, holly, oak, pawpaw, sweetgum, and zelkova.