Fireblight is a destructive disease of apples, crabapples, pears, cotoneaster and mountain ash. Infection usually occurs in spring when the trees are flowering or during the growing season after a hail storm. The disease causes the flowers and fruit to wilt, dry out and turn dark colored. Branches or stems may be killed back just a few inches or completely. Diseased leaves and fruits hang on fireblight-killed branches throughout the summer and fall.

Several things can be done to control or prevent fireblight. Planting apple varieties with some resistance is important. Avoid heavy use of fertilizer and water, as this promotes succulent growth which is very susceptible to fireblight. Spraying with Streptomycin is very important in preventing the disease. Start spraying when you can see the pink of the flowers and repeat every 4 to 7 days for a total of three sprays. If the bloom period is long, a fourth spray may be needed at petal fall.

Prune off the diseased parts of the tree in early spring or late fall. Do not prune during the growing season unless the disease is progressing rapidly down a branch and may reach the trunk. When pruning, cut 8-12 inches below the edge of the infected area or canker. After each cut, sterilize the pruner by dipping it in a solution of 1 part bleach and 9 parts water. Non sterilized pruners will spread the disease as you prune. Paint all pruning wounds with a pruning paint or latex house paint.

This page was last updated May 2003

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