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Verticillium Wilt

Maple trees get hit hard by this fungus

By: Sandy Feather 2012
Penn State Extension


Q. I lost a maple tree to verticillium wilt last year. I would like to plant another tree in that area, but am concerned because I understand the disease persists in the soil for many years. Are there any trees I can plant there that would be safe from verticillium wilt?

A: Verticillium wilt is a fungal disease that affects many deciduous trees and shrubs, as well as herbaceous ornamentals and certain vegetables. Conifers appear to be resistant. The fungus stays dormant in the soil until it enters a susceptible plant through wounds in the roots or base of the tree. It clogs the water conducting vessels in the infected plant, reducing the flow of water to branches and leaves.


WILT SYMPTOMS

Symptoms of verticillium wilt include heavy seed production, smaller than normal leaves, browning on the margins of the leaves, and branch dieback. It is not uncommon for one side of an infected tree to be wilting or dead while other side appears to be healthy. Another common symptom is the discoloration of the wood under bark of wilting branches. Healthy sapwood is white. If it is infected with verticillium, the sapwood may have dark green, black or reddish-brown streaks. The color of these streaks depends on the species of tree. Newly infected or small branches may not exhibit this symptom.

Dogwood
Dogwoods are resistant to Verticillium Wilt

Large trees can live for a long time with the infection, but most trees die in two or three years. The management of mildly infected trees includes protecting them from road salt and drought stress, and a moderate fertilization program that avoids high nitrogen applications. Research into fungicide injections has shown that some populations of verticillium fungi are more susceptible to control than others.

 


PRECAUTIONS

Avoid using wood chips from verticillium-infected trees as mulch or in potting mixes because the fungus can survive mix and infect other plants that are mulched with them or planted into the potting mix.


REPLACEMENT CHOICES

Planting resistant species where verticillium wilt has been a problem is the best way to deal with this disease. Species that have shown resistance include: beech (Fagus spp.), birch (Betula spp.), boxwood (Buxus spp.), hickory (Carya spp.), katsura tree (Cercidiphyllum japonicum), hornbeam (Carpinus spp.), dogwood (Cornus spp.), hawthorn (Crataegus spp.), ginkgo (Ginkgo), honey locust (Gleditsia triacanthos var. inermis), holly (Ilex spp.), larch (Larix spp.), sweetgum (Liquidambar styraciflua), crabapple (Malus spp.), sycamore (Platanus spp.), white oak (Quercus alba), pear (Pyrus spp.), and walnut (Juglans spp.).
  


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