The most common disease is leaf spot, and the worst insect pests are aphids. Check the plants regularly and control aphids with insecticidal soap sprays. Leaf spot is a fungus that's especially prevalent in areas where the weather is warm and moist. Small spots with light centers appear on plant leaves, eventually causing the leaves to turn yellow and drop off. To control leaf spot, rotate crops, plant certified disease-free seeds, remove and burn damaged leaves, and stay away from plants when they're wet.
Nematodes are microscopic eel-like creatures that can be beneficial or harmful.
Several species of nematodes plague southern gardeners, stunting plant growth, killing root systems and cutting down yields. In addition to feeding on plant roots, they may also carry and spread disease. Stunted, yellowed and wilted plants are symptomatic of nematode damage. Preventive measures include crop rotation and adding loads of organic matter to your garden before planting. For information on nematode control in your area, contact your Extension Service agent.