EB – Early Blight
Scientific Name: Alternaria solani
Type: Fungus
Early Blight is a soil-borne disease that affects the growth of tomatoes. This disease is most common in North America. The symptoms include collar rust on the stems, circular dark spots appear on the leaves, rings surround the spots with a yellow halo, and tomatoes crack at the stem. The leaves may die and fall off the plant resulting in extensive defoliation, exposing the tomatoes to sun scald. Black spots may appear on the tomatoes. The disease can cause substantial yield loss and total crop loss. It is spread by wind and water. The infected plants should be removed and burned to avoid further infestation. The virus can live in plant debris and in the soil. The disease is favorable when temperatures are 82-86 F and usually occur when moisture and humidity are very high. Plan on using a 2 to 3 year crop rotation and avoid planting in the same location, year after year, and can survive in the soil for 1 year. Fungicides can help manage the disease. Stake plants to improve air circulation. Use drip irrigation to keep foliage dry and avoid overhead irrigation. The best option is to use virus-free seeds and disease resistant varieties
LB – Late Blight
Scientific Name: Phytophthora infestans
Type: Oomycete
Late Blight is a fungal disease that affects the growth of potatoes and tomatoes. Symptoms include large dark brown blotches with a green gray edge on the leaves resulting in large sections of dry brown foliage. Stems become dark brown. Dark brown circular spots cover most of the tomato. The entire field turns brown and wilted as if it was hit by frost and die.It can cause significant yield loss and even total crops losses. The diseased tomatoes are usually unmarketable. Late blight was responsible for the Irish potato famine of the late 1840s. The air-borne disease can destroy an entire field in a short period of time. The infected plants should be removed and burned to avoid further infestation. If you stick with Late Blight resistant tomato varieties you don’t have to worry. The disease is favorable when temperatures are 60-70 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 the soil for 7 years. Fungicides are available for management of late blight on tomatoes. 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.