Bacterial Leaf Spot

• Xanthomonas campestris pv. vesicatoria is one of the bacteria responsible for bacterial leaf spot disease, a general term for spot diseases caused by bacteria. Several related bacteria can cause similar symptoms. Bacterial leaf spot begins with tiny yellow spots or brown spots with yellow halos appearing on the plants. The spots typically dry out and form holes in the leaves or cause the leaves to crumple. Defoliation may eventually occur. Bacterial leaf spot also affects fruits, which develop small brown wart-like bumps visible on the skin and on the interior of the pepper flesh. Some strains of these bacteria affect tomatoes, potatoes and other garden plants in the nightshade family.
  
  

Cercospora Leaf Spot

• Cercospora leaf spot is caused by a fungus. It is characterized by dark spots on the leaves and stems of affected pepper plants, sometimes a half-inch in diameter. The spots may be circular or oval-shaped, often lighter in the center with darker margins. This fungus is seed-borne, with the spores spread by the wind.
  
  

Treatment

• Copper hydroxide in a bioavailable form is the recommended organic treatment for both black leaf spot and cercospora leaf spot. Manganese ethylene bis is an alternative chemical fungicide for cercospora. Gardeners should apply either as directed on a 7- to 10-day schedule.
  
  

Prevention

• Good garden sanitation helps control both bacteria and spores in the garden. Garden debris and nearby weeds can serve as host plants where pathogens can overwinter, so weed control and cleanup are a must. Use well-aged compost to avoid spreading soil-borne spores throughout the garden. Organic gardeners can reduce the chance of perpetuating seed-borne disease by selecting the best fruits from healthy plants that show no signs of disease. Use these fruits as the source of your saved seeds. Avoid keeping volunteer pepper plants. Although they may appear hardy and healthy, young volunteer plants may carry either soil-borne or seed-borne diseases that will manifest later in the season. Crop rotation is an effective way to curtail disease host plants. Proper fertilization helps you grow pepper plants with healthy immune systems that can resist diseases.