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PROGRESS AND EVENTS
by
John Wilson

County Extension Agent for Agriculture and Nature Resources University of Kentucky , College of Agriculture
For more information, contact John Wilson at...
859/623-4072 or e-mail jowilson@uky.edu

May 31, 2006

ANTHRACNOSE DISEASE ON LANDSCAPE TREES
Cool, wet weather in spring favors the fungi that cause anthracnose diseases in landscape trees. Symptoms of infections that occurred during recent weeks are appearing in several tree species. Although anthracnose diseases are common this year on landscape trees and also on some fruit crops, they are not all caused by the same fungus. Each host plant has its own anthracnose fungus, so, for example, don't assume that anthracnose of sycamore or grape is a threat to nearby dogwoods. The incidence and severity of anthracnose diseases of landscape trees varies with the season, and this year, symptoms appear to be at moderate levels.

Ash anthracnose. Brown blotches along leaflet edges have been visible for the past week or so on new ash foliage. Many of these infected leaflets will begin to drop soon and carpet the walks and lawns nearby. Ash anthracnose is not normally a threat to ash tree survival, however, and the ash trees will simply put out a new set of leaves. The ash anthracnose fungus is a species of Discula.

Dogwood anthracnose. Caused by the fungus Discula destructiva, dogwood anthracnose is appearing this spring in many Kentucky flowering dogwoods (Cornus florida ). Dogwood anthracnose causes leaf spots, leaf blight, and lower branch dieback and is most commonly observed in forested regions where native understory dogwood trees are threatened. This spring, anthracnose is also present in landscape trees, especially those growing in shaded locations.

Maple anthracnose. Symptoms can range from leaf spots to shoot blight and shoot cankers. Maple anthracnose may be caused by Discula sp. or by Kabatiella apocrypta. Leaf spots with brown, somewhat angular symptoms associated with Kabatiella are being observed most commonly now. There is considerable variation in maple susceptibility to anthracnose. In some cases, sugar maple leaf spotting may be heavy on one tree while the adjacent tree is barely affected.

Oak anthracnose. This disease is less common here and is caused by the fungus Apiognomonia quercina.

Sycamore anthracnose. Anthracnose symptoms have become noticeable on sycamore in the past week. On infected green, expanding leaves, look for irregular dark, necrotic blotching centered along the leaf veins or leaf edges. These dark blotches may turn a tan color as the diseased areas of the leaves dry out. In the same trees, tips of young shoots with newly expanding leaves are wilting and dying because of twig or shoot infection. With continued rainy weather, the disease should continue to spread in the foliage. Symptoms are not as severe as we see some years when trees are heavily defoliated by now. As the weather gets warmer and drier, sycamores normally put out new, healthy foliage. However, the legacy of crooked branches (because lateral shoots take over when terminals are killed by anthracnose) and multiple shoots arising from the base of a killed branch may still be visible many years later. Sycamore anthracnose is caused by the fungus Apiognomonia veneta, and the fungus attacks both sycamore and London plane.

RETIREMENT TIME HAS COME
By now most of you have heard I am retiring at the end of May.  The last 35 years with the Cooperative Extension Service has been great.  The last 31½ years were here in Madison County . 

I have had the opportunity to work with many of you over the years and for those opportunities, I am grateful.  The farm field days, county livestock tours, Master Gardener programs, out-of-state summer tours, cattle sales, and the list could go on and on.  I always enjoyed answering your calls and office visits. 

Over the next several months an agriculture agent from surrounding counties will be in the office one day per week to continue to answer your questions.  Also, co-workers will help as well. 

I plan on continuing to live in Madison County , and be active in the county.  Again, it’s been a great 31½ years serving the residents of Madison County . 

John Wilson, Madison County Extension Agent for Agriculture and Natural Resources

859/623-4072 or e-mail jowilson@uky.edu.

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