A – Anthracnose
Scientific Name: Colletotrichum lagenarium
Type: Fungus
Anthracnose is a world-wide fungal disease that affects the growth of cucumbers, tomatoes, and watermelons. This disease is most common in the southern, mid-Atlantic, and mid-Western parts of the United States. Symptoms include lesions on the leaves and then yellowish circular spots begin appearing on the leaves. On watermelons the spots are irregular and turn dark brown or black. The most striking symptom is circular, black, sunken cankers appear on the fruit. When moisture is present, the black center of the lesion is covered with a gelatinous mass of salmon colored spores. With tomatoes, the disease mainly affects the tomato, but also can infect leaves, stems and roots. Sunken water soaked circular spots appear on the tomatoes. Leaves show symptoms of small circular spots with yellow halos. It can cause significant yield loss and even total crops losses. The diseased tomatoes are usually unmarketable. The infected plants should be removed to avoid further infestation. Increase space between the plants to maximize air flow and drying of the leaves. The disease is favorable when temperatures are 75-82 F and usually occur when moisture and humidity are very high. Plan on using a 3 year crop rotation and avoid planting in the same location, year after year, as the disease can survive in over winter on crop debris. Proper tillage practices may be helpful in managing the disease. Fungicides can help manage the disease. The best option is to use disease resistant varieties.
F – Fusarium Wilt (Race 1)
Scientific Name: Fusarium oxysporum
Type: Fungus
Fusarium Wilt, Race 1, is a fungal disease that affects the growth of tomatoes. It is one of the most devastating of all soil-borne diseases. Race 1 is the most widely found throughout the United States, especially in warm regions of the country. It attacks the roots of the plants and moves up the stems. Symptoms include yellowing and browning of the older bottom leaves, stunting, and wilting. Often the entire plant will die. Usually little or no fruit develops. The infected plants will produce inferior and unmarketable tomatoes. It can cause significant yield loss and even total crops losses. If you stick with Fusarium Wilt Resistant tomato varieties you don’t have to worry. Many of the older heirlooms don’t have any resistance to the disease, so if you grow these then you should keep an eye out for it. The infected plants should be removed and burned to avoid further infestation. Plan on using a 5 to 7 year crop rotation and avoid planting in the same location, year after year, as the disease can survive in the soil up to 10 years. The best option is to use disease resistant varieties.
N – Root-Knot Nematode
Scientific Name: Meloidogyne spp.
Type: Parasites
Nematodes are soil dwelling parasites that feed on plant roots and affect cucumbers, okra, peppers, squash, and tomatoes. Symptoms include yellowing of the leaves, wilting, and stunting of the plant. The plant will have galled and decayed roots. Nematodes are most active when soil temperatures are 85 - 95 F and usually occur when the soil is moisture. Plan on using a 3 year crop rotation and avoid planting in the same location, year after year. Nematodes are most active in warm soils and they need water to thrive so take advantage of summer’s heat to wither them away. Withhold water from nematode infested areas of the garden and turn or till the soil every 7-10 days during the summer to expose nematodes to the drying effects of the sun. Proper tillage practices may be helpful in managing the disease. Certain types of marigolds work by excreting a substance that is damaging to nematodes as well as trapping them in their roots and preventing reproduction. Elbon rye is an effective nematode control that can be planted as a cool season cover crop that is turned under in early spring. The use of soil fumigants like Vapam has been helpful and a fungicide called Actinovate can also be helpful in managing the lowering of the nematode population. Using transparent plastic mulches for 4 to 6 weeks have been shown to kill nematodes. The best option is to use disease resistant varieties.
St – Stemphylium Gray Spot Leaf
Scientific Name: Stemphylium solani, Stemphylium floridanum, and Stemphylium botryosum
Type: Fungus
Stemphylium Gray Spot Leaf is a fungal disease that affects the growth of tomatoes. It is found in warm regions of the country, and is common in the Southeastern part of the United States. Symptoms include brown to black specks on leaves. As the lesions grow in size, they develop a gray center surrounded by a yellow area. The spots may dry and fall out, forming a shot hole in the leaf. The disease may cause the entire leaves to turn yellow, then brown, and drop off, and the plant may be stunted. The tomatoes are not usually affected unless there is severe defoliation, where sunburn damage can occur on the tomatoes. If you stick with Stemphylium Gray Spot Leaf Resistant tomato varieties you don’t have to worry. Many of the older heirlooms don’t have any resistance to the disease, so if you grow these then you should keep an eye out for it. The infected plants should be removed and burned to avoid further infestation. Plan on using a 5 to 7 year crop rotation and avoid planting in the same location, year after year, as the disease can survive in the soil for many years. Stake tomato plants for better circulation. Give plants extra space to allow air to move among leaves to keep leaves as dry as possible. Use soaker hoses and avoid overhead watering. The best option is to use disease resistant varieties.
V – Verticillium Wilt
Scientific Name: Verticillium dahliae
Type: Fungus
Verticillium Wilt is a soil-borne disease that affects the growth of lettuce, peppers, spinach, and tomatoes. This disease is most common in the United States and Europe. In lettuce symptoms include wilting of the lower leaves and then the outer leaves turn yellow, wilt and die. Brown and black streaks appear on the taproot and crown The disease can cause substantial yield loss and total crop loss. It is a seed-borne disease that is spread by farm equipment, wind, and water. The infected plants should be removed and burned to avoid further infestation. The virus can live in weeds, so use weed management techniques. The fungus is very difficult to eradicate once it has been introduced into a field. Plan on using a 4 year crop rotation and avoid planting in the same location, year after year, and can survive in the soil for 14 years. Keep the fields weed free. Deep tilling may be helpful in managing the disease. Thoroughly clean equipment after working in a field. Fumigate fields with methyl bromide. The best option is to use virus-free seeds and disease resistant varieties