Disease

Fire blight

Erwinia amylovora

A bacterial disease of pear, apple, crabapple, mountain ash, hawthorn and their relatives. It enters through flowers in warm, wet spring weather, kills blossoms and shoots, and can run down into the main limbs and trunk.

Signs

• Blossoms, leaves and shoots turn black or brown as if scorched, and the dead leaves hang on.
• Shoot tips bent over like a shepherd's crook.
• Cream to amber ooze on cankers and shoots in warm, humid weather.

What favors it

Warm, wet weather during bloom (above about 65 °F, 18 °C), hail or wind damage, lush growth from heavy nitrogen, and susceptible varieties.

Prevention

• Plant resistant varieties of pear, apple and crabapple.
• Go easy on nitrogen; soft, fast shoots blight fastest.
• Remove root suckers and water sprouts, and prune out cankered wood in the dormant season, at least 8 inches below the canker.

Crops it shows up on

Apple, pear & stone fruit; Shade & ornamental trees; Roses & ornamentals.

Often confused with

Sources

• Fire BlightMontana State University Extension
• Fire blightUniversity of Minnesota Extension
• Fire Blight in Ornamental Trees and Shrubs (2.907)Colorado State University Extension

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