Sample of the week (November 12, 2018): Elm anthracnose

elm anthracnose

The plant clinic received Chinese elm sample diagnosed with black leaf spot, a fungal disease caused by Stegophora ulmea. Black leaf spot also described as elm anthracnose disease appears as small tan, brown, black or tar-like spots on upper leaf surface. As the disease progresses, spots may coalesce to form unevenly-shaped leaf blotches. Elm anthracnose is mostly common about the time for normal leaf fall and may not cause serious damage to trees. In severe infection, elm anthracnose can cause premature defoliation of susceptible trees. Repeated defoliation may cause weakness, increase susceptibility to diseases and eventually death of the tree. The pathogen overwinters in infected buds and plant debris. During cool and moist weather conditions, spores are discharged and spread by wind and rain. This disease can be managed by raking infected plant debris and pruning dead wood to reduce inoculum build-up for future infection.