The Q&A Archives: Anthracnose

Question: I have some recently relocated silver lindens about 6 ft tall that one is doing well and the other looks to be suffering from Anthracnose. I cannot find the appropriate chemical to spray this tree with. Problem is that new foilage looks like it is drying up and falling off and old foilage looks like window screen with all the holes in it. No bugs or fungus seen. What is the pro's recommendation?

Answer: Typically, you'll see blighted leaves (discolored) with anthracnose, not holes in the leaves, so I'd caution you to have a professional diagnosis before assuming the problem is anthracnose. You can take leaf samples to the Cooperative Extension office or Master Gardener clinic in your area.

Anthracnose rarely causes significant damage to shade trees; consequently specific control measures generally are not required. Nevertheless, the disease may be unacceptable in certain high visibility landscape settings. The disease also can increase susceptibility to other disease or insect problems in areas where trees are attacked year after year.

Several cultural practices can reduce the severity of anthracnose. Removal of dead leaves in the fall will help limit the amount of fungal inoculum present for infection of new leaves the following spring. However, this practice rarely eliminates the problem, especially for those anthracnose fungi that may also survive in blighted twigs on the tree.

Proper tree spacing and placement to promote good air circulation reduces the number of hours leaf surfaces remain wet, and decreases the likelihood of fungal infection. Many trees recover rapidly from anthracnose if they are maintained in a vigorous condition.

Trees should be watered and fertilized regularly. In some cases, nitrogen fertilization may actually increase the tree?s tolerance or resistance to anthracnose.

There is considerable variation in the susceptibility of various tree species or cultivars to anthracnose. For example, London Plane is more resistant to anthracnose than sycamore; red oaks tend to have fewer problems with the disease than the white oak group; and there appears to be variation in individual elms and black walnuts to their respective anthracnose diseases. Avoid planting highly susceptible trees in areas with poor air circulation.

Chemical sprays normally are not necessary to control anthracnose. Occasionally, trees with a history of anthracnose may require treatment for aesthetic purposes. Several fungicides are labeled for certain anthracnose diseases.

Thorough coverage and proper timing of the sprays are essential for adequate control. Begin applying a fungicide at bud swell and make 1 to 2 additional sprays at 10 to 14 day intervals. Early sprays are critical for control.

Bordeaux, Daconil, Fungi-Gard, Liquid Fungicide, Encore, and Monterey Bravo are registered for control of anthracnose.

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