EB0983

VERTICILLIUM WILT OF MAPLES

Verticillium wilt is a common dis- maples may die quickly, or may live ilized tools to avoid fungus spread. ease of many different kinds of plants for years. Sterilize shears or other pruning tools including ornamental (landscape) The disease can be more posi- in rubbing alcohol after pruning in- plants, fruit trees, and vegetables. In tively identified by cutting lengthwise fected portions of trees. Washing the western Washington, the disease is into the trunk or an affected branch. In pruning tools in soap and water be- especially common on maples, par- living wood, olive-green streaks are fore sterilizing, if practical, is a good ticularly the smaller ornamental usually present (Fig. 1). In dead wood, idea. maples. The disease is often serious, less distinct brownish streaks are usu- The fungus can also be spread if causing reduced plant beauty, reduced ally present. This streaking may be lo- the infected branches are not properly growth, or death. cated anywhere in the wood, and may destroyed. Destroy the removed The leaves on diseased maples be found more commonly in the roots branches by burning, or place them in may suddenly wilt and die, or may sud- or lower trunk, but is usually present the garbage or take them to the dump. denly drop at any time during the grow- in the branches also. The olive-green Apply only limited amounts of ni- ing season. These symptoms may streaks should not be confused with trogen fertilizer, just enough to insure occur over the entire tree, or only on those occurring around wounds in normal growth. However, there are one side, or only on one or several healthy trees. conflicting reports as to the benefit of branches. The leaves may or may not This disease is caused by the fun- applications of high nitrogen fertilizer. be stunted and yellowed. Diseased gus Verticillium albo-atrum. The fun- Be sure to water the tree as neces- gus generally invades the plant sary. through the roots, but can also infect Completely remove dead trees or through wounds on the aboveground shrubs, including the root system; de- parts of the plant, causing the symp- stroy as mentioned previously. This will toms mentioned above. The fungus dispose of a great deal of the fungus can survive in the soil for many years, and lessen its spread, but some of the even after the diseased plant has been fungus will still be in the soil. There- removed. fore, avoid moving any soil from the Wilting, dropping, yellowing, or contaminated area to uncontaminated stunting of leaves, especially over the areas. Remember that the fungus can entire tree, may occur simply because survive in the soil for many years. Any of poor care of the tree, and Verticil- tools (such as shovels, shears, saws, lium wilt may not be involved. Always etc.) which were used in the removal be sure to give your maple good cul- of the infected plant should be cleaned tural care. and/or sterilized to avoid spreading the fungus. CONTROL Although the fungus can infect Verticillium wilt is not effectively many kinds of plants, some plants are controlled by chemicals, but there are considered resistant or immune to Ver- some cultural control measures which ticillium wilt. Such plants don’t often can help. become diseased. If you want to plant Prune out and destroy affected an ornamental or landscape plant in branches. Be sure to prune back to an area known to be contaminated by wood which shows no streaks, and be Verticillium, then choose a resistant or Fig. 1. careful to make the final cut with ster- immune plant.

COOPERATIVE EXTENSION Some plants regarded as resistant or Quercus spp. (oaks); Crataegus spp. planes); Betula spp. (birches); conifers immune to Verticillium wilt: many (hawthorns); Liquidamber styraciflua (such as yews, firs, pines, etc.); and Cornus spp. (dogwoods); Juglans spp. (sweet gums); Salix spp. (willows); monocots (such as grasses, irises, lil- (walnuts); most Malus spp. (apples Platanus spp. (sycamores and ies, daffodils, tulips, gladioluses, etc.). and crabapples); Pyrus spp. (pears);

Prepared by Roy M. Davidson, Jr., former Research Technologist, and Ralph S. Byther, Extension Plant Pathologist, WSU, Puyallup (retired).

College of Agriculture and Home Economics, Pullman, Washington

Issued by Washington State University Cooperative Extension and the U.S. Department of Agriculture in furtherance of the Acts of May 8 and June 30, 1914. Cooperative Extension programs and policies comply with federal and state laws and regulations on nondiscrimination regarding race, color, gender, national origin, religion, age, disability, and sexual orientation. Evidence of noncompliance may be reported through your local Cooperative Extension office. Trade names have been used to simplify information; no endorsement is intended. Reprinted October 1997. Subject code 255. A. EB0983