Are the leaves on your ash or maple tree falling off? Do the fallen leaves have brown or black areas on them? This leaf drop may be caused by a fungus called Anthracnose. It commonly attacks the leaves of certain trees during wet cool weather.

Just as the trees start to leaf out in the spring, the disease will cause tiny dark spots on the new leaves. When the disease infects the leaves before they are fully expanded, they may show puckering and crinkling around the diseased areas. If the infection is severe the trees may drop their leaves and then re-leaf out again within a few weeks. Generally the second set of leaves won't become infected by the disease unless our weather is still wet and cool.

Controlling anthracnose on large trees is usually too expensive and generally not necessary unless the trees have been severely infected with the disease for the past few years. Fertilize infected trees to help them maintain their vigor and keep them well watered during periods of drought. Raking up the fallen leaves may help control the disease.

Young trees which are just getting established may benefit from a fungicide application to prevent further infection. Even though it won't cure the leaves which are infected, it will prevent the disease from spreading to healthy leaves. If they have lost their leaves from anthracnose, spray with a fungicide just as the next set of leaf buds are opening and every 10-14 days as needed. Hopefully this will prevent the fungus from damaging the new leaves.

This page was last updated May 2003

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