The barberry tree is just one of hundreds of trees and food crops that verticillium wilt attacks. This fungal disease feeds on woody and herbaceous plants, including viburnum shrubs, landscape trees and food crops, and can spread throughout a plant, eventually killing it. Some signs include stunted growth, dying branches or wilted, scorched-looking or brown leaves. Fungicides cannot control the disease.
Select healthy, disease-resistant stock to keep verticillium wilt out of the garden. The Ohio State University Extension Service lists several trees that appear resistant to the disease, including mountain ash, beech, birch, sweet gum and holly trees. Certain red maples also fare well against verticillium wilt. OSU Extension recommends looking for these cultivars: Scarlet, Red Sunset, Schlessinger, Armstrong, Autumn Flame, Bowhall and October Glory. Fir, mulberry, hackberry, juniper, sycamore and willow also are immune or resistant to the disease, says University of Minnesota Associate Professor of Plant Pathology Cynthia Ash.
Verticillium wilt mimics many other diseases and conditions, including herbicide damage. A laboratory test of a tissue sample can confirm the disease, the University of Minnesota's Ash says.
Trees and plants that exhibit recent, moderate symptoms might survive with proper care. Ash says those plantings fare better in "moderately fertile soil," which has a high potassium and low nitrogen content. Make sure the plants receive adequate water and trim off any dead or dying stems or branches, she adds.
If you must remove trees or plants, replace them with disease-resistant varieties and destroy or dispose of all debris. Don't use any mulch from a diseased plant unless it has been heated in a compost pile or by other means to destroy the fungi, Ash says.
The disease-causing fungi, either Verticillium albo-atrum and Verticillium dahliae, live in soil. In some cases, soil fumigants can destroy the fungi at the source, although they will do nothing to "cure" an infected tree or plant, Ash notes, adding that this measure works best in small gardens. Fumigants have several disadvantages, according to the American Phytopathological Society. They are expensive, some types can harm the environment and their use is restricted in some areas, the APS says.
Effective soil fumigants include chloropicrin, chloropicrin-methyl bromide mixes, Vapam and Vorlex, according to the University of Illinois Extension.