Plant Health Problems
Diseases caused by Fungi:
Damping-off, Pythium sp., Rhizoctonia solani, Sclerotinia sclerotiorum.
This disease is a rotting of the roots and the base of the stem so that the seedling falls over and dies. Damping-off is caused by a number of different fungi which live in the soil and may attack seedlings of almost any crop. Pepper seedlings are particularly susceptible to damping-off. The disease is favored by high soil moisture and cool temperatures.
To avoid damping-off, start seedlings in pasteurized soil or use soilless potting mix, give them only enough water to keep the plants growing normally, and ventilate the growing space during the day. The use of fungicide-treated seed can also reduce damping-off. Once plants are beyond the seedling stage, they are no longer susceptible to damping-off.
Phytophthora blight, Phytophthora capsici.
The disease can appear anytime when wet conditions prevail. The disease has two different phases. A crown rot phase develops when plants are grown in wet infested soils and is characterized by stunting, chlorosis, and wilt. The foliar phase appears when wind-driven rain blows inoculum up onto the foliage, stem, and fruit and causes blackened lesions which can coalesce and kill the plant.
Fungicides are relatively ineffective. The fungus requires at least 48 hours of wet conditions to cause disease. Plant on well-drained soil and practice rotation with plants that are not in the nightshade or squash families. Among the compounds registered for use in Connecticut are maneb and metalaxyl. Consult the label for dosage rates and safety precautions.
Pythium root rot, Pythium sp.
Infected plants resemble the crown rot phase of Phytophthora blight. Plants appear stunted and wilted with water-soaked tissue at the stem base. The disease can appear in wet, poorly-drained soils.
Plants should be hilled on well-drained soil. Control can be achieved by improving water drainage in the field and using a two-year rotation with nonsusceptible plants, such as corn, to prevent the buildup of pathogenic organisms.
Anthracnose, Colletotrichum nigrum.
On either green or ripe pepper fruits, this disease shows as dark, circular, sunken spots which vary in size, but may be an inch or more in diameter. The surface of the spots is covered with black dots which contain the spores of the fungus. After rain or heavy dew, pinkish masses of spores exude from these dots. Infected fruits may be completely rotted away and fall from the plants. They may also cling to the plants as withered "mummies." Diseased fruits serve as sources of spores which wash and splash around to infect other fruits. Anthracnose is a soil- and seed-carried disease which also infects and survives on stems and leaves through the season. On stems and leaves, the symptoms are usually so slight that the plant does not appear diseased until fruits develop.
It is usually not important enough in Connecticut to require spraying. Among the compounds registered for use in Connecticut is maneb. Consult the label for dosage rates and safety precautions.
Diseases caused by Bacteria:
Bacterial spot, Xanthomonas campestris pv. vesicatoria.
The disease is caused by a bacterium and appears on stems, leaves, and fruit. Lesions first appear on the underside of leaves as small circular lesions that are raised up slightly. Lesions can enlarge to 0.4 mm and develop necrotic centers with yellow halos. The bacterium is seedborne and is spread on wind-driven rain.
Infested seed can be treated with hot water (125 F for 25 minutes). Sanitation practices should include using clean pots and trays and burying infected residues in the fall. The disease can also be suppressed with the use of copper fungicides applied when symptoms are visible. Consult the label for dosage rates and safety precautions.
Diseases caused by Viruses:
Pepper plants with mosaic have mottled leaves and small, bumpy, off-color fruit. The diseased plants are usually stunted and have smaller leaves than normal. The symptoms on the fruit may include light-colored ring-spots or target-spots. Mosaic on pepper may be caused by a number of different viruses alone or together. These viruses also infect tobacco, tomato, cucumber family crops, alfalfa, clover, and many other crops and weeds. Most of these viruses are carried by aphids. Some of the viruses may last in crop refuse for a long time, and may sometimes be carried by merely touching a healthy plant after touching a diseased plant. Other viruses attacking peppers do not last very long in crop refuse and are carried only by insects.
To avoid mosaic on pepper you should control insects; do not plant next to tomatoes, cucumbers, tobacco, alfalfa, or clover; and pull up and destroy plants showing symptoms.
Pepper plants may be infested by at least three different species of aphids: the melon aphid, Aphis gossypii, green peach aphid, Myzus persicae, and the potato aphid, Macrosiphum euphorbiae. They are not usually a problem except when insecticides have eliminated their natural enemies. See Aphid fact sheet.
European corn borer, Ostrinia nubilalis.
These caterpillars may feed on the fruit, particularly if corn and pepper are planted adjacent to each other. This insect feeds not only on corn, but also on other crop plants, many weeds, and on a variety of other herbaceous plants. The larvae tunnel in the pepper fruits. The larva is pale white or gray with black tubercles and is not more than 1" long when fully grown. Adults have a wingspread of an inch or so and are buff to brown. There are usually two generations annually.
Control begins with tillage of the plant stubble, either in the fall or early in the spring. This reduces the survival of borers from the previous year. Pheromone traps may be used to monitor flight of the adults. Among the compounds registered for control of this pest in Connecticut are Bt formulations. Bacillus thuringiensis var. kurstaki (Bt), in either a granular or liquid formulation, may be applied to the top of the plant so that it flows down onto the developing peppers. Additional applications may be needed when caterpillars or signs of feeding damage are visible, or when pheromone traps indicate the flight of adults. Consult the label for dosage rates, safety precautions, and preharvest intervals.
The parasitic wasp Trichogramma has been used as alternative method of control. This tiny wasp attacks the egg masses of the corn borer, and the eggs of other caterpillars, too. Be sure to purchase the insects from a reputable supplier and make sure the strain you purchase is known to be well adapted to attacking corn borer. Bt will not harm the Trichogramma wasps, but other insecticides will.
This small, black, active beetle may feed on newly set plants early in the season. Control is not usually needed.
Pepper maggot, Zonosemata electa.
The maggots of these barred-wing flies infest the fruits of peppers, causing them to decay, and in eggplants, resulting in tunneling within the fruit. The eggs are deposited in late July and August in the wall of the fruit and often project into the interior cavity. They hatch in 10 days and feed inside the core until mature, a period varying from 12 to 22 days. They then make an exit, usually near the stem in peppers, and go into the ground and pupate 1 or 2" beneath the surface. There is one generation a year. The adult fly is light yellowish-brown in color, with three brown bands across each wing. The adults feed on nitrogenous materials (perhaps bird droppings) in trees near pepper or eggplant fields. Damaging infestations are patchy and sporadic in Connecticut, and limited to fruit developing during the brief period (2-3 weeks) when egg laying occurs. The gardener does not usually recognize the problem until it is too late for control.
Stalk borer, Papaipema nebris.
These dirty grayish caterpillars, which are darker with white stripes when young, bore in the stems of pepper. The eggs of this caterpillar are laid in the fall by the moths on surrounding grasses and weeds. After hatching in the spring the borers feed on these plants and later may migrate into adjacent fields where they cause injury. The caterpillars are very active. Their restless habit of frequently changing from one plant stem to another increases the damage. Keeping the borders of the vegetable garden well-mowed and controlling weeds may help deny these insects their breeding grounds.