Late Blight Detected in Genesee County
Written by Alex Feig on August 20, 2019
BATAVIA – Late Blight was detected in Genesee County on August 16. Late blight is a serious, airborne disease of tomatoes and potatoes best known for causing the Irish potato famine. Late blight is caused by a fungus-like organism that spreads dozens of miles on storm fronts.
Late blight can kill plants in less than two weeks. Disease spots are often dark gray to brown in color and tend to be surrounded by pale green tissue. Initially, spot shape and size varies but eventually most of an infected leaf or stem will become discolored and die. Leaf spots often look slightly fuzzy on the underside of the leaf in the early morning or when the weather is wet and humid conditions. Late blight will put dark brown to black smears on plant stems. Tomato fruit may also develop large, firm, greasy-looking, brown, gray, or black smears on the upper part of the fruit. Potato leaves show dark spots with fuzzy white spores on the underside during humid weather. Potato stems show similar lesions to those seen in tomato.
Late blight does not resemble lower leaves that yellow and contain numerous small black specks. Late Blight does not leaves to have spots that contain small, black, concentric rings.
Since this disease is aggressive, spreads easily, and can be very damaging to area farmers, Cornell Cooperative Extension asks that anyone suspecting they have late blight please contact their local CCE office for assistance with identification. In Genesee County, home gardeners may contact the Master Gardener Helpline at 585-343-3040 x 127. Samples may be dropped off at the office, 420 East Main Street, Batavia, from 9 am to 3:30 pm. Please put them in a clear, plastic bag. Commercial vegetable farmers may contact the Cornell Vegetable Program – cvp.cce.cornell.edu/specialists.php.
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