Green peppers can contract disease from insects, human handling and excessive moisture. A healthy plant serves as the best protection against these diseases. But being able to recognize a problem early may help you treat the plant and still harvest healthy fruit in late summer.
Bacterial spot manifests as small, blister-like spots as large as 1/4-inch in diameter on either or both the leaves and fruit of the green pepper. These spots later turn brown and warty. Control of this disease after establishment is difficult; the best tactic is to buy clean seed from a reputable company or buy a resistant cultivar of green pepper. This disease can survive in the soil for one to two years, so crops should be rotated to avoid infecting new plants.
Anthracnose, also called ripe fruit disease, is one of the most common rots found on peppers. It manifests as sunken lesions reaching an inch in diameter. The small, raised specks within the lesion are actually live spores of the fungus. During rainy periods and periods of high humidity, this disease spreads quickly to other plants. You can attempt to control anthracnose by applying a fungicide to young fruits, but this will not work with moist weather.
Cercospora Leaf Spot
Cercospora leaf spots appear as large round or oblong red spots with dark red borders on the leaves, stalk or stem of the green pepper plant. Severely infected leaves lose their ability to feed themselves, subsequently turn yellow and drop off the plant. This leaves the fruits bare, exposing them to sun scald injury. Remove and destroy infected plants immediately and treat your other plants with a fungicide if the infection persists.
Mosaic consists of a number of different diseases that mottle and distort the leaves of the pepper plant. Aphids most often transmit the disease, so controlling them will help decrease infection. Pull out any weeds around the garden as well to eliminate an aphid sanctuary.
Blossom-end rot only affects the fruit of the green pepper plant. When infected, a decaying spot develops on the blossom end of the fruit and gradually spreads. This usually occurs when the pepper is 1/3 to 1/2 grown. This disease is thought to be caused by a calcium deficiency in the soil as well as fluctuation in soil moisture. To control blossom-end rot, keep the soil evenly moist and apply fertilizer and calcium-nitrate to the soil.