Key Features
- Leaf drop/ purple leaf spots
- Spots may have dead centers
- Black bumps in center of spots
Symptoms
Septoria causes light brown to dark purple spots that begin on the upper surface of host leaves. These spots develop grey to tan centers with tiny black bumps. Severe infections may cause defoliation. Several years of defoliation may lead to a decrease in the number of leaves that emerge in following years. Cercospora leaf spots occur on flowering dogwood and Cornelian cherry (a dogwood), and produces angular, tan to reddish-brown spots.
Biology
The fungus survives on leaf litter from plants infected the previous season. Warm, wet spring-like weather promotes spore production and dispersal. Spores landing on a susceptible host in the presence of high relative humidity or water on the leaves are likely to infect and cause disease. Spots grow and the fungus produces spores within the dead, tan centers. These spores may be splashed to healthy tissue, spreading the disease. Neither leaf spot poses a threat to the plants health and survival.
Management Recommendations
Whenever possible, reduce overhead watering, and keep leaves as dry as possible. Thin the canopy or planting to increase air circulation. Correct fertilization, irrigation, and soil drainage will increase plants' natural defense against the disease. Remove and destroy all infected plants and plant debris to reduce the spread of disease. Several fungicides are labeled for homeowner use for the control of Septoria leaf spot, however, these fungicides can only prevent new infections. Always read and follow the directions on the product label.vd
Effective Pesticides
Active Ingredients include: Chlorothalonil, Copper salts, Myclobutanil, Sulfur
Resources
- Not satisfied with ID? Contact the Purdue Plant and Pest Diagnostic Lab
- Sign Up for the Purdue Landscape Report
