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The presence of the two mating types allows the disease to overwinter in the soil without tomato or potato plant tissues. For sexual reproduction to occur, two mating types- A1 and A2- must be present. The number of strains present is not as important as whether or not two mating types occur. Photo: Gerald Holmes, Strawberry Center, Cal Poly San Luis Obispo, Advanced symptoms of late blight on tomato Late blight in Maryland 2009 outbreakĪ number of strains of Phytophthora infestans were identified from different east coast states in 2009. Infected tomato and potato plants often decline rapidly and die.Įarly foliage symptoms of late blight Late blight lesion on a tomato stem.When the infection is severe, a foul odor is produced in both crops. Infected potato tubers develop a dry, corky rot that often shows up in storage.Infected tomato fruits develop shiny, dark, or olive-colored lesions which may cover large areas.S tem lesions appear brown to almost black.Under favorable conditions, a white fuzzy mold will appear on leaf undersides that contain the spores of the pathogen.Dead leaves typically remain attached to stems. These spots enlarge until the entire leaf or stem turns brown and dies. Lesions develop on leaves and stems as dark, water-soaked spots.When plants are infected with late blight: Late blight is sometimes brought into the garden from infected transplants and seed potatoes. The most recent widespread infections in home gardens occurred in 19. Gardeners in cooler areas of Maryland are more likely to see late blight symptoms. The disease is slowed down by a return to hot, dry weather. Disease spores are spread short distances by rain and very long distances by wind. Late blight can occur at any time during the growing season when the weather is cool and wet. This is the same disease that caused the Irish potato famine in the 1840s. Late blight is a potentially destructive water mold or fungus-like disease that can affect tomatoes and potatoes in Maryland fields and gardens. What is late blight and how does it spread? If you suspect late blight on your tomato or potato plants, please submit close-up photos through the Ask Extension service.USABlight is a national project to monitor for late bright outbreaks.It can become active in cool, wet weather.The disease affects all parts of tomato and potato plants.Late blight (Phytophthora infestans) is the devastating water mold disease that caused the Irish potato famine in the 1840s.Timely application of the fungicide is very important.

Alternating the fungicides helps in preventing the pathogen from developing resistance towards either of them.Whenever conducting any foliar spray, mix the fungicide with INTEGRA 3ml/20l in order to improve its efficacy.CADILAC 800WP 50g/20l (for prevention purposes).The following fungicides are effective against early blight disease. This method of control involves the use of chemicals (fungicides). These lesions could be covered with a mass of black fungal growth as infection progresses. Fruits that are infected with this disease have lesions which appear leathery and may also contain the concentric rings.Infection continues even in storage causing the tubers to shrivel. Tuber tissue is usually dry, brown and leathery. Infected tubers develop dark sunken lesions which are usually surrounded by a purple-like raised margin.On stems, lesion start as small, dark and slightly sunken regions which enlarge as infection continues.Infected leaves become chlorotic then necrotic and this may cause defoliation. These lesions are dry and papery and develop characteristic concentric rings of raised and necrotic tissue as infection progresses. Brown lesions develop on older leaves.Spores invade the plant tissues either through direct penetration or through injured/damaged areas.ĭespite its name ‘early blight’, symptoms usually develop on the older leaves, mostly, nearing the end of the season. Older leaves and those under stress are more susceptible. The fungus produces a lot of spores under cool and moist conditions which are then blown by wind or splashed by water to adjacent plants to initiate infection.Įvery part of the crop can be infected with this disease, eventually forming lesions.

The pathogen overwinters in infected plant materials in the soil or even on solanaceous weeds. The disease can also occur on other solanaceous crops like eggplant, capsicum etc. Early blight is a fungal disease caused by a fungus Alternaria solani, which mostly affects tomato and potato plants, causing significant losses if not effectively controlled.