Stems: Symptoms include collar rot, stem cankers, and brown lesions with dark concentric circles. Spots are black and can have concentric circles. Solanaceous weeds (black nightshade- Solanum pytcanthum, hairy nightshade- Solanum physalifolium)įruit: Fruit rot is a common symptom.Most frequently on tomatoes and potatoes.Infected seed can also be the cause of diseased plants. Once the initial infections have occurred, they become the most important source of new spore production and are responsible for rapid disease spread. New spores are produced the following season and can be transported by water, wind, insects, animals, and machinery. If the infected plants are not removed at the end of the season, the fungus can spend the winter in infected plant debris in or on the soil where it can survive at least one or perhaps several years. Infections are most prevalent on poorly nourished or otherwise stressed plants. The optimal temperature range for sporulation is about coupled with abundant moisture (as provided by rain, mist, fog, dew, or irrigation) is present. After penetration, lesions may form within 2-3 days, or the infection can remain dormant awaiting proper environmental conditions ( and extended periods of wetness). Another 3 to 12 hours are required for the fungus to penetrate the plant depending on the temperature. This disease causes direct losses by the infection of fruits and indirect losses by infection of stems, leaves, and reduction of plant vigor.Īlternaria spores begin to germinate within 2 hours over a wide range of temperatures but at the optimal range of 80☏ to 85☏ it can only take a half hour. Pathogen: Alternaria solani, Alternaria tomatophilia IntroductionĮarly blight of tomato, caused by the fungus Alternaria solani, is perhaps the most common foliar disease of tomatoes in the Northeast and is also common on potatoes and other nightshades. Alicyn Smart, Assistant Extension Professor & Extension Plant Pathologist and Katherine Ashley, Graduate Student, University of Maine.įor information about UMaine Extension programs and resources, visit .įind more of our publications and books at /publications/. Bruce Watt, Extension Plant Pathologist, University of Maine Cooperative Extension Clemson U-USDA CES Slide Series, Bugwood.Originally developed by Dr. Of the fungicides listed in Strategy 6, consult the Organic Materials Review Institute (OMRI™) for appropriate organic copper products.Įarly blight on tomato fruit and foliage ( Lycopersicon)Įarly blight on tomato leaf ( Lycopersicon)Įarly blight on tomato leaf ( Lycopersicon). Using an appropriate organic fertilizer would be a viable organic approach to Strategy 2. Strategies 1, 3, 4, and 5 are strictly organic approaches. Apply at fruit set and reapply every 7–14 days. Effective fungicides include copper (Kocide), chlorothalonil (Bravo, Daconil), mancozeb, or maneb. Disease is more readily spread when plant foliage is wet.Ħ. Confine staking and picking to times when foliage is dry. Avoid planting eggplant or potatoes where tomatoes were last planted.ĥ. Pull weeds that compete for light, water, and nutrients, especially nightshade, horse nettle, and other weeds in the tomato family.Ĥ. Remove plant debris or till it into the soil. Do a thorough cleanup of the garden in the fall. Water the plants regularly, but don't fertilize until the plants are well-established and in full blossom. Stressed plants are more susceptible to early blight. These varieties will require a less intensive management program than susceptible varieties.Ģ. Varieties such as ‘Early Cascade’, ‘Floramerica’, ‘Jetstar’, ‘Manlucie’, ‘Supersonic’, and ‘Surecrop’ have some tolerance to early blight. Spores thrive in moist, warm temperatures (80–90 degrees F) and can persist in partially decomposed garden waste for at least a year.ġ. Fungal spores enter a host through wounds in the plant cuticle. Spores are spread by wind and rain, but occasionally, flea beetles transmit this disease. This disease typically progresses from the base of the plant, upward.Įarly blight spores survive on old plant debris or in the soil. Early blight can result in extensive defoliation, exposing fruit to sunscald and reducing yields. The entire leaf may be killed and will drop off the plant. Eventually, the spots enlarge into a series of concentric rings surrounded by a yellow area. The appearance of circular or irregular dark spots on the lower, more mature leaves is one of the first symptoms of infection. Infection on leaves is the most common symptom. Plants infected with the fungus can display collar rust on the stems, infected older leaves, and fruits that crack at the stem. Early blight can affect seedlings but is generally observed on older plants and is especially severe on plants of poor vigor. Early blight is a fungal disease, Alternaria sp., that occurs on tomatoes throughout North America.
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