Left: A pair of ash trees photographed in May. The tree on the left is partially defoliated by ash anthracnose. Despite unsightly leaf drop, damage to ash trees is not usually severe.
Right: A close-up of anthracnose damage to ash tree leaves. The most serious damage to this tree occurs in late spring.

For more complete diagnosis and treatment information, visit https://ohioline.osu.edu/hyg-fact/3000/3048.html

1. Overall tree care program. Use proper fertilization, pruning, watering, and pest control practices to encourage vigorous plant growth. This aids in general tolerance of the effects of disease and in rapid refoliation in years where disease is severe.

2. Fungicide applications. If significant damage occurs yearly and controls are justified, properly applied fungicides may reduce damage from these diseases. High pressure spray equipment will be needed for large tree applications, and this typically requires the hiring of a professional tree care service. Fungicides will not be effective unless they are applied before and during infection periods. Typically, three applications are necessary, beginning in early spring, with the first application made before leaf buds open. Applications in the fall have been shown to be useful for sycamore anthracnose control. Fungicide injections have also shown promise for sycamore anthracnose control. These must be applied by professional tree care companies. Some common product names containing the fungicides include: mancozeb (Fore, Dithane, Mancozeb), chlorothalonil (Daconil*, Bravo, otho-multipurpose fungicide), thiophanate-methyl (Cleary’s 3336, Domain) and propiconazole.

It is always the pesticide applicator’s responsibility, by law, to read and follow all current label directions for the specific pesticide being used.

Anthracnose diseases are generally not severe on maple, but can cause considerable unsightliness from brownish leaf blotches and some leaf drop when moist weather conditions make the disease particularly severe. When fungicides are required, use labeled products containing mancozeb, thiophanate-methyl, or chlorothalonil.

This anthracnose disease is primarily a leaf blighting and blotching disease of white ash and, to a lesser extent, green ash. When fungicide is required, use a labeled material containing thiophanate-methyl, chlorothalonil, or mancozeb.

White oaks are the most susceptible of many oak species to this leaf blotching disease. Fungicides are generally not recommended. If fungicide is required, use a labeled material containing thiophanate-methyl, chlorothalonil or mancozeb.

This is a potentially serious disease of American sycamore and to a lesser extent London planetree. Fungicide applications to prevent infections in the spring are sometimes warranted. If fungicide is required, use a labeled material containing thiophanate-methyl, chlorothalonil or mancozeb. Fungicide injections (which are made by tree care professionals) are also used in spring and fall to systemically control the disease.

In recent years this disease has become prominent in certain areas, especially on flowering dogwood (Cornus florida). Dogwood anthracnose is most severe where cool, moist conditions occur during the summer, such as in higher elevation areas, and in densely vegetated shady sites with poor air movement. When fungicide is required, use a labeled product containing propiconazole or mancozeb.

72-96 – Hours from beginning of infection period that some fungicides are most effective on apple trees.

50-60 – Rate percentage (of full rate) that some fungicides can be reduced to without appreciable risk unless rainfall is frequent. Source: Penn State College of Agricultural Sciences