Green pepper plants, or Capsicum annuum, grow up to 2 feet high and prefer full sun, a reflection of climate conditions in their native Central and South America. Gardeners in the United States and Canada can strive to provide green peppers with a healthy environment--not too wet and humid--so the plants thrive and produce shiny fruits about 75 days after transplanting.
Bacteria, soil-borne molds called water molds or oomycetes, fungi and viruses can cause disease in green pepper plants.
Bacterial leaf spot manifests as leaf spots on the lower surfaces of leaves. Spots may become purplish gray with black centers, have narrow yellow halos and enlarge to 1/4 inch in diameter, according to the Penn State College of Agricultural Sciences. Many leaves turn yellow and eventually drop off. Cercospora leaf spot, also known as frogeye leaf spot, manifests as spots with light-gray centers. Southern blight turns pepper plants yellow and finally brown after a sudden wilt. Anthracnose manifests as sunken circular spots on green and ripe fruit. Viruses cause leaf mottling, curling or puckering, deformed fruit and stunted plants. Water molds lead to fruits covered with white, dusty-looking fine mold.
Home gardeners can purchase pepper seed from a reputable seed company to acquire seed free of spot bacteria, suggest horticulturalists at the Institute of Food and Agricultural Sciences at the University of Florida. Check transplants from a retail nursery carefully for symptoms of bacterial spot and avoid purchase of diseased plants. Use raised beds if your vegetable plot has problems with drainage, buy varieties known to be resistant to diseases in your area and control perennial weeds that may spread disease, suggests New Mexico State University.
Home gardeners can use copper-containing fungicide for some control of bacterial spot diseases. Destroy plants with frogeye leaf spot promptly when the season ends to avoid carryover, the University of Florida recommends. For commercial growers, greenhouse sanitation, crop rotation and especially clean seed comprise the key components for controlling pepper diseases, especially bacterial leaf spot, according to Thomas A. Zitter of the Department of Plant Pathology at Cornell University. Seeds can be treated with hot water or bleach just before treatment for control.
Avoid tobacco products when working around pepper plants to lessen the risk of transmitting tobacco mosaic virus, and wash hands and tools in milk to sharply reduce transmission of the disease, recommend plant pathologists at the University of Florida.