(WIVB) — Late blight has been detected in three western New York counties this week.

Chautauqua County officials say it was found in Cattaraugus, Allegany and Genesee counties.

Late blight, which is best known as the cause of the Irish Potato Famine, can kill plants in one week.

Characteristics of the disease are dark gray or brown spots that may be surrounded by rings of pale green tissue. The spots are irregularly shaped and could become the size of a quarter.

Fuzzy, white spores underneath leaves in wet and humid conditions are also signs of late blight.

A plant’s stem will have dark brown or black smears that look like “someone took a small, muddy paint brush” to it, the Cornell Cooperative Extension of Chautauqua County (CCE) says.

Tomatoes may also have greasy-looking, gray, brown or black smears on the upper part of the fruit if it has the disease.

Late blight is a very aggressive disease caused by a fungus-like organism. The CCE says it “spreads dozens of miles on storm fronts.”

Anyone who thinks they have seen late blight can call their local CCE office. The Chautauqua County one can be reached at (716) 664-9502.

Commercial vegetable farmers can call the Cornell Vegetable Program at (585) 406-3419.