Key Features
- Discolored spots
- Well-defined dead spots
- Some defoliation is possible
Symptoms
Leaf spot is a general term describing diseases that cause spots on leaf surfaces. These spots can range from white, yellow, red, purple or black discoloration, to dead or missing spots. Exact symptoms vary greatly depending on the host, pathogen, and environment. Leaf spots may also be caused by fungi, bacteria, foliar nematodes, insects, nutrient deficiencies, or physical injury.
Biology
Leaf spot pathogens typically survive between seasons on diseased leaf litter. Most infections on shrubs and shade trees rarely cause permanent damage. However, repeated severe infections can reduce strength and cold hardiness. Many anthracnoses and blights first appear as leaf spots but also cause damage to stems; these are generally more damaging.
Management Recommendations
General recommendations for managing leaf spots are the same, regardless of pathogen and host. Maintain space around each plant to enhances air circulation, irrigate below the canopy if possible (drip irrigation) or water only in the morning when leaves have the most time to dry. Collect and destroy leaf litter before buds break in the spring to decrease the amount of the pathogen in the landscape. Keep weed and plant-feeding insect populations low; these can harbor diseases and help them spread. In some cases, resistant cultivars are available. Chemical control varies depending on host and pathogen. If necessary, have a plant disease diagnostic lab identify the disease before applying fungicides. Only use fungicides on hosts/ pathogen combinations listed on the product label. Read the label carefully--certain fungicides can damage some hosts. See specific disease profiles for more information.
Effective Pesticides
Pesticides are neither available nor recommended for managing this disease.
Resources
- Not satisfied with ID? Contact the Purdue Plant and Pest Diagnostic Lab
- Sign Up for the Purdue Landscape Report
