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Fire Blight of Apple and Pear

Fire blight is destructive to apple and quince trees and is the most serious pear disease in the eastern United States. In recent years, significant losses to the apple industry have resulted due to this disease.

Bacteria overwinter in the margins of cankers on branches and trunks. When the temperature reaches about 65°F, bacteria begin to multiply and appear on the outsides of the cankers in drops of clear to amber-colored ooze.

Temperatures just before and during bloom will determine if fire blight becomes serious in early spring. Daily temperatures must average 65°F or higher during pink through petal fall for bacterial populations to grow enough to cause severe disease. The disease also occurs later in the season when bacteria enter late-opening blossoms or growing tips of new shoots.