Bacterial spot is the most common and economically important disease of peppers in Kentucky. The disease occurs in commercial and homegrown production. Disease damage to leaves results in yield reduction, while diseased fruits become unmarketable. Cultural and sanitation practices can help reduce disease severity, but chemical management may be needed to protect plants from infection.
Bacterial Spot Facts
- Symptoms begin as small, brown, circular spots that overtime expand and may develop an angular appearance. Lesions may develop on leaves (Figure 1), stems, petioles, and fruit (Figure 2). The center of older lesions on leaves may become white and fall out, leaving a “shot-hole” appearance. Infections of petioles often results in defoliation. Spots on fruit may be either sunken or raised depending on cultivar.
- Disease is introduced via contaminated seed, crop debris, or from weed hosts.
- Bacterial spot is spread by water, such as overhead irrigation or rain.
- Periods of wet, warm, humid conditions favor disease development.
- Once bacterial spot establishes in a planting, it can spread rapidly.
- Bacterial spot is caused by multiple bacterial Xanthomonas species.
Management
- Purchase certified disease-free seeds or transplants.
- If saving seed from a previous season, heat treatment should be used to disinfest seed.
- Select resistant varieties.
- Manage weeds in or near plantings.
- Rotate crops.
- Increase plant spacing.
- Remove and destroy infected plants or plant parts.
- Avoid overhead watering.
- Prune plants to improve air flow.
- Monitor and manage humidity in greenhouses and high tunnels.
- Clean and sanitize tools, pots, and equipment.
- Remove and destroy plant debris and discarded fruit at the end of the season.
- Preventative copper applications are recommended for commercial production.
Commercial growers can find information on fungicides in the Vegetable Production Guide for Commercial Growers (ID-36) and the Southeast U.S. Vegetable Crop Handbook. Homeowners should consult Home Vegetable Gardening (ID-128) for fungicide information or contact a county Extension agent for additional information and recommendations regarding fungicides.
Additional Resources
- Bacterial Spot of Pepper & Tomato (PPFS-VG-17)
- Managing Greenhouse & High Tunnel Environments to Reduce Plant Diseases (PPFS-GH-1)
- Greenhouse Sanitation (PPFS-GH-4)
- IPM Scouting Guide for Common Pests of Solanaceous Crops in Kentucky (ID-172)
- Home Vegetable Gardening (ID-128)
- Vegetable Production Guide for Commercial Growers (ID-36)
By: Kim Leonberger, Plant Pathology Extension Associate, and Nicole Gauthier, Extension Plant Pathologist
Kentucky Pest News 