Spot Anthracnose on dogwoods
By Peyton Sapp
Greene County Ag Extension Agent
It will not be long before spring arrives. Once it does arrive we will get to see an explosion of color. One of the first landscape trees to provide you with this color will be your dogwoods. Dogwoods usually bloom from late March through mid April.
Why, you might ask, are we discussing dogwoods blooming? Well, there is a fungus that can cause your dogwoods to get the disease Spot Anthracnose. This is one of the most common diseases of the dogwood. I often get samples of the disease in the extension office. Spot Anthracnose is fairly easy for you to spot and often looks terrible.
The first part of the tree to be infected by the Elsinoe corni fungus is usually the flower bracts. Leaves, young shoots and fruit can also be infected. The first symptoms of the disease can be detected as circular or elongated reddish-purple spots approximately one mm in diameter on the flower bracts. As additional infections occur, the spots become more numerous and merge together. Severely infected flower bracts can become distorted and may fall off prematurely. The infection then moves to the foliage.
I suppose that I have made Spot Anthracnose sound like a terrible, terrible disease. Well, the truth is that it is not necessarily a "deadly" problem. The fungus lives from year to year in infected fruit and tissues. Other parts of the plant can be infected from bud break, about mid March, through leaf emergence, late in June. Now, weather plays a big role. If the weather is dry before and/or during the flowering period, then very little disease will occur. This is why the severity of Spot Anthracnose varies from year to year.
p>So, have you seen this disease in your dogwoods in the past? If you have and are interested in working to control the problem, you must start your program before you see symptoms. In many cases you will not need to use a fungicide spray. Typically, the disease will not result in decline or death of your dogwoods. If the appearance of the disease is a problem for you then there are several fungicides that you can use. Chlorothaloil, mancozeb, or another labeled fungicide applied at budbreak (around mid-March), full bloom (earl April) and leaf emergence can give 75-85 percent control. It is not feasible or practical to treat many large trees.
Removing fallen leaves and limbs is another way for you to provide some control of the disease. By doing this you will remove some of the material that harbors the fungus. You take away the source of infection for the next year.
Not everyone has a problem with Spot Anthracnose on dogwoods. Even if your dogwoods have the disease, it may not mean that you have a serious problem. Evaluate your situation and determine whether you nee to use a fungicide treatment. While you are evaluating, think about the severity of the disease last year, the weather patterns and your landscape management program. You may decide Spot Anthracnose is not that big of a problem.
If you would like more information on growing dogwoods in your landscape contact your local County Extension Office.
Peyton Sapp if extension agent for Greene, Morgan and Putnam Counties.