Key Features
- Brown, coalescing spots
- Lesions on stems or scapes
- Blighted appearance
Symptoms
Early infection of young, immature leaves often results in dead and/or deformed leaf margins as well as dead, irregularly shaped spots that tend to form along the veins or be confined by them. Heavily infected leaves may appear misshapen and curled. Mature leaves are more resistant to infection. Older leaves develop small, brown spots when infected in the summer during wet weather. Infections are most abundant in the crown and may involve the stipe/stem of infected plants. Tiny bumps (fruiting bodies) may be seen within or underneath spots. A hand lens or magnifying glass is usually required to see these.
Biology
Warm, wet weather, promotes infection of all these pathogens. The fungus survives between seasons on fallen leaves and stems, and in the crown of perennials. In the spring, spores are blown or splashed from stem spots to developing leaf and twig tissue. Infected leaves may shrivel and fall, while infected young stems can be girdled and killed. High relative humidity and leaf wetness are required for these pathogens to cause new infections. Symptoms are most severe in the lower canopy where humidity is highest and leaves are not dried by the sun.
Management Recommendations
Anthracnose may be ugly, but does not cause permanent damage to most well-established plantings. it can be a regular problem on certain perennials, like lily-of-the-valley, ivy, hosta, and perennial ornamental grasses. Proper watering, mulching, and sanitation procedures will reduce damage caused by anthracnose. Raking and removing leaves in the fall will reduce the number of new infections the following year. Fungicide application should begin at bud break to protect new growth. Repeat applications according to the fungicide label during cool, wet weather. Read the label carefully and apply only as directed.
Effective Pesticides
Active Ingredients include: Chlorothalonil, Copper salts, Myclobutanil, Propiconazole, Tebuconazole, Thiophanate-methyl
Resources
- Leaf Diseases
- Not satisfied with ID? Contact the Purdue Plant and Pest Diagnostic Lab
- Sign Up for the Purdue Landscape Report
