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.