Fire blight on pears

Fire blight is a bacterial disease -- not fungal -- that makes pear branches die in a distinctive hook shape, as if the tips were scorched. It spreads through open blossoms during warm, wet spring weather, moving from flower to flower faster than most gardeners realize is possible. Pears are more.

Fire blight is a bacterial disease — not fungal — that makes pear branches die in a distinctive hook shape, as if the tips were scorched. It spreads through open blossoms during warm, wet spring weather, moving from flower to flower faster than most gardeners realize is possible. Pears are more susceptible than apples; some European pear varieties have essentially no resistance and require intensive management in most of the eastern US.

I don't grow pears at my Long Island property, so this guide draws on Cornell Cooperative Extension, Penn State Extension, and Clemson HGIC research.

The pathogen

Fire blight is caused by the bacterium Erwinia amylovora. Per Cornell Cooperative Extension, this North American native infects the entire apple family (Rosaceae: pears, apples, quince, serviceberry, hawthorn, crabapple, mountain ash) and is considered one of the most destructive bacterial plant diseases in the world.

The bacterium overwinters in cankers on infected wood — dark, water-soaked areas at the margins of blighted tissue. In spring, bacteria ooze from these cankers and are carried by rain, insects, and wind to open flowers.