Peppers, eggplant, and okra are troubled by a few diseases, especially in the South. Peppers and eggplant are related to tomatoes, so they're susceptible to many tomato diseases as well as some of their own.
Keep plants healthy. This starts with soil that is rich in humus, drains well, and has ample nutrients. Amend soil regularly with compost and apply organic mulches continually to enrich your soil. Test soil samples for nutrient levels and pH, and make necessary adjustments. Apply only as much fertilizer as you need, since excess can cause growth imbalances that weaken plants and invite disease. Cull plants that are diseased to prevent pathogens from spreading.
Plant disease-resistant varieties. Look for varieties of peppers, eggplant, and okra that are resistant to wilts and other diseases. Disease resistance is noted in seed catalogs and seed packets. If you purchase seedlings, ask nursery staff to point out their disease-resistant stock.
Control pests. Keep a close watch for pests, especially aphids and leafhoppers, which can spread diseases as they feed. Their feeding can also create entry points for rot organisms. Also, plants that are weakened by pests are more susceptible to disease.
Weed your garden. If you allow weeds to get our of hand in your garden, the competition for nutrients and moisture can weaken crop plants, leaving them susceptible to infection. Crowding also reduces air circulation, allowing moisture to remain on plants long enough to allow fungal and bacterial pathogens to infect plants. (Though you may be tempted to keep the area surrounding your garden mowed, a diverse array of plants in your yard invites beneficial organisms that help control pests.)
Water judiciously. Water-stressed and overwatered plants are vulnerable to disease. Since pathogens spread more rapidly among wet plants, drip irrigation is the most efficient way to water. It doesn't moisten leaves and stems, saves water, and puts it in the root zone where plants need it. If you do use overhead sprinklers, water during the early morning so your plants have time to dry before nightfall. Also, stay out of the garden when it's wet to avoid spreading disease yourself!
Rotate crops. Since some diseases are soilborne, planting crop families in different beds each year improves their chances of avoiding problems and reduces the amount of the pathogen in the soil. A three-year rotation with other plant families is recommended.
Manage crop residues. If plants are healthy, spade or till plant residue into the soil, or add it to your compost heap. This clean-up work helps by removing overwintering spots for pests, and the addition of organic matter improves the soil. If plants suffered disease, it's better to burn the plant residue or bury it in a spot far from the garden.
The descriptions below will help you identify diseases affecting your crops. By following the recommended controls you may be able to catch the problem early on and check their progress.
Leaf spot shows up in various forms: leaves, stems, or roots develop small, yellowish-green to brown spots; old leaves may show water-soaked spots; fruit develop small, raised rough spots or rot spots, or fruit may fail to set. There are a few leaf spot diseases caused by various seed- and soil-borne fungi and bacteria. Control measures include use of disease-free seed, crop rotation, and avoidance of overhead watering.
Anthracnose appears on fruits as dark circular, sunken spots with black spores. It's a seed- and soil-borne fungus that can also be transmitted by infected plant debris. To control, use disease-free seed, do not cultivate when plants are wet, and rotate crops.
Mosiac symptoms include green-yellow mottling of leaves, which become curved and distorted; the plant is usually stunted; fruits are yellow or wrinkled with dark spots, or are small, bumpy, and off-colored. Aphids transmit the virus that causes mosaic. Gardeners may carry it from infected areas, and the disease can live on crop refuse. To control it, destroy infected plants, do not use tobacco while in the garden, wash hands with soap and water before handling plants, control insects that transmit the disease, and use resistant varieties.
Blossom end rot appears as a black, sunken ring on the base of a fruit. It's different from the other diseases because it's not caused by an organism, but by a nutrient deficiency. Large fluctuations in soil moisture can make roots unable to take up adequate calcium, and the cells at the fruit's growing tip die. To avoid blossom end rot maintain soil pH between 6.0 to 6.8, and maintain adequate, regular moisture by improving soil, spreading mulch, and watering deeply and evenly when needed.
Root knot nematodes produce galls (knots) on okra and pepper roots, which stunt and weaken plants. Root-knot nematodes are microscopic worms that live in the soil and can be transmitted on seeds. To control nematodes, rotate crops with grasses or legumes, and maintain a high level of soil organic matter.
Wilts show up as wilting leaves and plants, and eventually plants die. Fruits are few, small, and of poor quality. Wilts are caused by various fungi that live in the soil or on crop residues. Control via crop rotation, a high level of soil organic matter, and good drainage.
Photography by Iowa State University Extension Plant Pathology
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