Common pepper disease
Leaf spots that appear on the lower surface of older leaves as small, pimples and on the upper leaf surface as small water-soaked spots are a symptom of bacterial spot. This is an important pepper disease in Maryland. It also occasionally attacks tomatoes. Eventually, the spots develop gray to tan centers with darker borders. Lesions enlarge during warm, humid weather. Leaves may then turn yellow, then brown, and drop. Lesions may also develop on stems. Fruits develop small, raised rough spots that do not affect eating quality. Severely infected leaves will drop resulting in the sunscald of peppers. Bacterial leaf spot is spread by splashing rain and working with wet, infected plants. This disease can defoliate plants during wet weather. Hot, dry weather slows the spread of this disease. The disease can come in on seed or transplants and can overwinter in crop residue and soil.
Photo: Gerald Holmes, Strawberry Center, Cal Poly San Luis Obispo, Bugwood.org
Photo: Howard F. Schwartz, Colorado State University, Bugwood.org
Management
You can minimize problems with bacterial spot by following these tips:
- Select resistant varieties
- Purchase disease-free seeds and transplants.
- Treat seeds by soaking them for 2 minutes in a 10% chlorine bleach solution (1 part bleach; 9 parts water). Thoroughly rinse seeds and dry them before planting.
- Mulch plants deeply with a thick organic material like newspaper covered with straw or grass clippings.
- Avoid overhead watering.
- Remove and discard badly infected plant parts and all debris at the end of the season.
- Spray every 10-14 days with fixed copper (organic fungicide) to slow down the spread of infection.
- Rotate peppers to a different location if infections are severe and cover the soil with black plastic mulch or black landscape fabric prior to planting.