Walnut Anthracnose Present

The Iowa Department of Natural Resources (DNR) is seeing a slightly higher than normal amount of walnut anthracnose this summer, causing some black walnut trees to yellow and lose their leaves earlier and more extensively than usual. 

Walnut anthracnose is a common fungal leaf disease. The fungus infects foliage and produces brown to black leaf spots, often followed by yellowing and premature leaf drop. Wet and humid weather favors disease development. Iowa’s prolonged wet conditions this growing season have provided favorable conditions for new infections. The fungus also occurs on other Iowa hardwood trees, including oak, maple, sycamore, ash, linden and hickory. 

Treatment for these trees is generally unnecessary, and healthy trees are expected to leaf out normally next spring.