Key Features
- Brown patches of leaves
- Large, dead leaf blotches
- Blotches with yellowish edge
Symptoms
Guignardia leaf blotch is a common and ugly disease of buckeye and horsechestnut. Large, irregularly shaped, dead spots or blotches with bright, yellow (chlorotic) margins appear in mid to late spring. These spots may cause leaf edges to crinkle or roll. The outer edges of the dead tissue may be peppered with black fruiting bodies. By the end of the growing season, most leaves will be covered in spots, making the tree ugly, even from a distance.
Biology
The disease survives between seasons on dead leaves that were infected the previous year. Young leaves are infected in mid to late spring. The fungus produces spores throughout the season which result in repeat infections within the canopy as well as on nearby buckeyes and horsechestnuts.
Management Recommendations
Remove leaf litter from all nearby buckeye and horsechestnut trees after the fall leaf drop. Increase air circulation and minimize leaf wetness by pruning to thin the canopy, maintain ample space between plants, and limit sprinkler irrigation to the morning hours so leaves can dry through the day. Chemical control is not recommended for control of Guignardia leaf blotch due to the difficulty and safety concerns associated with spraying large trees and because the disease does little to no long term damage to its host.
Effective Pesticides
Active Ingredients include: Chlorothalonil
Resources
- Not satisfied with ID? Contact the Purdue Plant and Pest Diagnostic Lab
- Sign Up for the Purdue Landscape Report
