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Late Blight—Phytophthora infestans
Late Blight is a very serious disease. If you suspect Late Blight in your garden, please contact the University of Maine Cooperative Extension, Pest Management Office at 800-287-0279Brown, leathery spots on the top and sides of fruit. In humid conditions, white mold also forms. Spots start out pale green, usually near the edges of tips, then turn brown to purplish-black. In humid conditions a fuzzy mold appears on the undersides of leaves. Black and brown spots appear and spread. In high humidity, entire vines can be killed very quickly.
Early Blight—Alternaria solaniDark, sunken spots on the stem end of fruits. One or two spots per leaf, each ¼ to ½ inch diameter. Spots have tan centers with concentric rings and yellow halos. Dark, sunken cankers at or above the soil line.
Anthracnose—Colletotrichum coccodesDepressed, circular lesions up to 5 inches in diameter on ripe fruit. As lesions mature, they develop concentric rings and become dotted with small black specks. In moist weather, masses of salmon-colored spores may form on the lesion surface.
Bacterial Spot—Xanthomonas campestrisFruit lesions start as tiny raised blisters. Lesions increase in size and become brown and scab-like. On leaves, stems and fruits, brown circular lesions, less than 1/10 inch in diameter.
Bacterial Canker—Clavibacter michiganensisDistinctive spots are white and slightly raised initially, then raised with dark-colored center and white halos, each about 1/16 inch in diameter. The white halo later turns brown. Leaflets begin to turn brown at the edges, then die back progressively toward the leaf midrib. Often only one side of a plant is affected at first, but symptoms eventually spread.
Tomato Leaf Spot—Septoria lycopersiciFruit is not affected, although sunscald can be a problem due to foliage loss. Numerous brown spots on leaves, each about 1/16 inch in diameter. They do not have a yellow halo and they do have black specks in the center. First symptoms are usually on lower leaves after the first fruit sets. Disease spreads from oldest to youngest growth.
White Mold (Sclerotinia stem rot)—Sclerotinia sclerotiorumFruit is not affected. Infected stems are soft with a light gray bleached appearance. White mold appears on plants during flowering. Hard, black sclerotia with white interiors form inside stems.
Blossom End RotFirst appears as a sunken, brownish black spot ½ to 1 inch in diameter at the blossom end of the fruit. Spots gradually increase in size. Blossom end rot is caused by a calcium deficiency related to fluctuations in available moisture.
SunscaldOccurs on green tomato fruit exposed to the sun. Initially a whitish shiny area, the bleached tissues gradually collapse, forming a slightly sunken area that may become pale yellowish and wrinkled as the fruit ripens. The killed tissue is invaded by secondary organisms which cause the fruit to decay.
CatfacingMisshapen fruit with irregular bulges at the blossom end and bands of leathery scar tissue. Catfacing is caused by cold weather at the time of blossom set. Catfacing is most common in the large-fruited "beefsteak" type tomatoes.
Fruit CrackingCracking is due to rapid fruit development and wide fluctuations in water availablity. Radial growth cracks radiate from the stem. Concentric cracks encircle the fruit, usually on the shoulders.
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Identification and Control Information (each will open in a new window)
Bacterial Spot and Bacterial Canker
Tomato Leaf Spot (Septoria)
Blossom End Rot
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[Photos, left to right: Robert Wick, University of Massachusetts, Bugwood.org; Division of Plant Industry Archive, Florida Department of Agriculture and Consumer Services, Bugwood.org; Department of Horticulture Website at Cornell University; Yuan-Min Shen, Taichung District Agricultural Research and Extension Station, Bugwood.org; Clemson University - USDA Cooperative Extension Slide Series, , Bugwood.org; Clemson University - USDA Cooperative Extension Slide Series, , Bugwood.org; USDA; Clemson University - USDA Cooperative Extension Slide Series, , Bugwood.org; Apsnet.org; Mary Ann Hansen, Virginia Polytechnic Institute and State University, Bugwood.org; Ufl.edu; Clemson University - USDA Cooperative Extension Slide Series, , Bugwood.org; Heinz USA Archive, , Bugwood.org; Heinz USA Archive, , Bugwood.org; UMass Extension; MU Extension Plant Diagnostic Clinic; William M. Brown Jr., , Bugwood.org; ISU Plant Disease Clinic; Division of Plant Industry Archive, Florida Department of Agriculture and Consumer Services, Bugwood.org; Mary Ann Hansen, Virginia Polytechnic Institute and State University, Bugwood.org; Iowa State University Extension; Tim Coolong, University of Kentucky; ; Patrick Byers, MU Extension; Howard F. Schwartz, Colorado State University, Bugwood.org; Queen's Printer for Ontario, 2009; Queen's Printer for Ontario, 2009; M.E. Bartolo, , Bugwood.org; Queen's Printer for Ontario, 2009; ; Univ of California Extension; Texas AgriLife Extension Service, Texas A&M System; Paul Bachi, University of Kentucky Research & Education Center, Bugwood.org ]It is the policy of the State of Maine to minimize reliance on pesticides. The Maine Department of Agriculture and the Maine IPM Council encourage everyone to practice integrated pest management and to use pesticides only as a last resort. The mention of pesticides in the fact sheets linked to these pages does not imply an endorsement of any product. Be sure that any product used is currently registered and follow all label directions.