Erwinia amylovora is the bacterium that causes fire blight, a destructive disease of apples, pears, and other rose-family plants.
Fire blight is a bacterial disease of plants in the family Rosaceae, especially apples and pears. Erwinia amylovora can enter through flowers, wounds, or natural openings, then multiply in plant tissues and move through shoots and branches. Infected tissue often turns dark and appears scorched, giving the disease its name.
Warm, humid weather and rain can favor spread during flowering. Bees and other insects may transfer bacteria between blossoms, while splashing rain and contaminated pruning tools can move the pathogen. Affected shoots may bend at their tips into a characteristic “shepherd’s crook.”
Fire blight is not the same as fungal diseases that also produce leaf or twig damage. It is managed through sanitation, removal of infected tissue, resistant plant varieties, careful pruning, and—in some settings—approved chemical treatments. Erwinia amylovora is a plant pathogen, not a usual human pathogen.