Disease and insects pose the greatest threat to growing tomatoes successfully, but most gardeners can avoid potential infections by rotating the location of their tomatoes each year, cleaning up the garden in the fall, and growing disease resistant plants. Listed below are the most common disease and insect problems you may face.
Anthracnose- a fungal disease caused by cool, wet weather. Plants develop dark, sunken patches with brown spots on leaves, stems and fruits. If infected, apply a copper or sulfur based fungicide every seven days. If not contained, remove and destroy infected plants.
Early Blight- a fungal disease spread by wind and rain. Lower leaves are attacked first, forming brown spots with concentric rings. Eventually entire leaves turn brown and drop. Spray a copper-based fungicide to prevent disease from spreading.
Late Blight- a fungal disease which is especially problematic when cool, moist nights are followed by hot, muggy days. Plants develop water-soaked spots that appear on lower leaves, then turn brown. White fungal spores may be visible beneath leaves. Destroy all infected plants.
Fusarium Wilt- a fungal disease found throughout the U.S. Leaves turn yellow, then brown and droop, with lower leaves usually affected first. Remove and destroy infected plants.
Verticillium Wilt- a fungal disease found throughout the U.S. Symptoms resemble fusarium wilt. Remove and destroy infected plants.
Nematodes- tiny worms that cause disease like symptoms. Infected plants are stunted, then turn yellow and wilt. Pulling up plants reveals roots with galls, swollen spots or excessive branching. To prevent, apply chitin to the soil.
Blossom-End Rot- a cultural condition rather than a disease. Fruits present with water-soaked spots on the blossom end of the fruit. The spots turn black or brown. To prevent keep soil evenly moist and mulched.
Tobacco Mosaic Virus- a viral disease spread by handling tobacco products and on tools and hands. Plants present distorted, yellow and green areas on leaves. It cannot be cured - remove and destroy infected plants.
Cutworm- 1 to 2 inch soil dwelling caterpillars of several species of moths. They feed at night and hide in the soil during daytime. Protect plants by surrounding them with a collar from a yogurt container or something slick which the worms cannot scale.
Hornworm- large green caterpillars, up to 4 inches or more in length, with a black horn on their tail. They devour the foliage, fruit, and stems of tomatoes. Handpick and destroy.
Whitefly- tiny white insects that feed underneath leaves and flutter erratically when disturbed. Their feeding weakens and stunts plants. Treat infestations by spraying with insecticidal soap.