Later, heavily infected leaves turn brown and die back from the tip. The best control for this disease is prevention. Thorough clean up of old leaves in the fall or spring before growth begins can significantly reduce new infections because the disease overwinters on infected leaves. Heavily infected leaf tips may be cut off. A protective spray of Captan or chlorothalonil will help reduce further infection.
Symptoms are numerous, small, raised, rust-colored spots on the leaves and stems .
Thorough cleanup of old plant debris in the fall helps to reduce the disease next season. Fungicide treatment now would be of little value. This is a disease that can kill entire potato and tomato plants in a few days under cool, wet weather. While late blight has occurred in the United States since 1992, the pathogen has become more important in the past 5 years. About that time a new variant of the fungus developed and spread across North America.