Growing tomato plants is an ideal way to save money on groceries, in addition to providing a rewarding hobby. Because tomatoes are vulnerable to various diseases and pests, home gardeners should be aware of common signs of an infestation. Many diseases and pests of tomato plants are hard or impossible to manage once they have taken over, so it's important to know how to prevent problems before they start.
Fusarium and Verticillium Wilt
The most damaging fungal diseases attacking garden tomato plants are fusarium and verticillium wilt. Wilt diseases are different from other infections because they don't show spots on leaves. Symptoms of tomato plants having these wilt diseases are older leaves that become yellow and wilt around midsummer. As the yellowing travels up a plant's stem, the whole plant eventually dies. Both of these diseases are soil-borne, but Fusarium can also originate from seeds, according to the University of Illinois Extension website. Although these wilt disease can't be controlled, gardeners can practice crop rotation, planting only tomato varieties that are wilt-resistant.
Late blight is a fungal disease in which lesions grow on leaves that are initially large, irregular and greenish-black. As the lesions enlarge, they turn brown and develop a white mold. This disease grows quickly under humid conditions, destroying much plant tissue. It produces large amounts of spores that attract healthy leaves, stems and fruit when the right climatic conditions are present such as cool nights and warm humid days. Late blight can be avoided by rotating tomato fields or using seed and transplants that are disease free. Spraying crops with a fungicide is also effective.
Gray mold is a disease that mostly attacks older tomato plants and usually occurs in greenhouses. It's a fungal disease that initially starts on dead leaves at a plant's base. A thick gray fungus grows on dead leaves as many spores develop which give an infected plant a cottony look. Leaves that are affected will collapse and shrink. The fungus then travels into a plant's stem and produces cankers. Signs of the fungus are tomatoes with water-soaked soft areas and a dark gray fungus growing on the infected spots. Fungal spraying helps to control the disease.
Curly Top Virus
Curly top virus, which is transmitted by beet leafhoppers, causes plants to turn a dull yellowish color and stop growing. Stems and leaves become stiff with fruit ripening prematurely. Upper leaflets turn a purplish color, particularly along the veins, causing a plant to be stunted. Chemical controls work and row covers can be used for protecting plants from leafhoppers. Keeping fields regularly weeded also helps control the problem.
Anthracnose is a fungal disease that involves a tomato showing small, sunken, water-soaked spots. The spots grow larger, becoming darker and depressed with concentric rings. Warm, humid weather can cause the fungus to penetrate fruit and completely destroy it. Although a tomato fruit can be infected when it's small and green, it doesn't show any noticeable wounds until it starts to ripen. The fruit then becomes more vulnerable as it matures. This disease can be controlled by practicing crop rotation, using well-drained soil and applying regular fungicides.