Homegrown tomatoes still warm from the sun are one of the joys of vegetable gardening. Unfortunately, tomatoes are not the most disease free vegetable we can grow. Sometimes the problems are the result of the weather which we can’t control. But there are some common diseases, which, if caught early, can be managed to reduce the effect on these delectable fruits.
Early Blight, a fungus that overwinters in the garden can affect the foliage, stems and fruits of tomatoes. Leaves may die prematurely exposing fruits to sunscald. Dark spots with concentric rings are symptoms of early blight. To reduce the chances of early blight, thoroughly clean tomato plant debris from the garden in the fall and get rid of it. There are fungicide sprays to help reduce the problem and prevent its spread if caught early.
Gray Leaf Spot affects only the tomato leaves. Small dark spots visible on both the top and underside of the leaves will enlarge and turn grayish brown. The centers of the spots crack and fall out and remaining leaf tissue turns yellow. Warm, moist conditions make gray leaf spot worse. Again, in the fall, clean all tomato debris from the garden and dispose of it. Select resistant varieties.
Septoria Leaf Spot is the most common foliage disease of tomatoes. Circular water-soaked spots gradually develop grayish white enters with dark edges. The light-colored centers distinguish this from other foliar diseases. Overhead watering and splashing rain spread the spores to new leaves. To control this disease, water at the base of the plant, not the leaves and avoid working with the plants when leaves are wet. Again, rotate crops and get rid of plant debris in the fall.
Verticillium Wilt is caused by a soil-borne fungus and can affect other vegetables besides tomatoes. Symptoms include yellowing and eventual browning between the leaf veins starting with older, lower leaves and discoloration in the stems. Sometimes leaves turn yellow, dry up and never appear to wilt. The disease affects the plant’s ability to take up water and the plant eventually dies. The fungus persists in the soil for many years. Rotating crops and selecting resistant varieties is crucial as is getting rid of the affected plants and good fall garden clean up.
Fusarium Wilt is a persistent fungus that is found worldwide. Like Verticillium Wilt, it prevents the uptake of water and nutrients and affects potatos, peppers and eggplants as well. Lower leaves turn yellow and die. The main stem, if cut lengthwise, will have dark brown streaks. The plant may not die but will be stunted and production poor. Again, look for resistant varieties, be careful to avoid damaging roots when cultivating, and rotate crops.
Anthracnose is a common, soil-borne fungus that causes tomato fruit rot. It starts with small, round sunken spots which increase in size and darken in the center. Wet weather encourages anthracnose. To reduce the potential for the disease, remove the lower 12 inches of leaves to avoid contact with the soil and try not to water the foliage. Mulch can help prevent soil splash.
Blossom End Rot is just that. Dark brown spots develop on the blossom end of the tomato and the tomato rots. This disease is caused by lack of calcium during fruit set if too much high nitrogen fertilizer is used or watering is uneven. The best solution to the problem is regular, deep waterings.
Catfacing, the scarring on the blossom end of the tomato, may come from insect damage, poor pollination or, the most common, temperatures below 50° during flowering and fruit set. During warmer temps, uneven watering may also cause catfacing. Heirlooms tend to be more susceptible to the problem. Catfaced tomatoes are safe to eat, just rather unattractive.
Growing tomatoes appears to be fraught with peril, but good garden sanitation, careful watering, and early identification of diseases can definitely improve the chances of a good crop.
More information is available from U of M Extension. Use this link: www1.extension.umn.edu/garden. For help with gardening questions, call 444-7916, leaving your name, number, and question. A local master gardener will call.
