Fire Blight
Erwinia amylovora
Overview
A highly destructive bacterial disease of apples, pears, and related rosaceous plants. Infected shoots appear scorched by fire, with characteristic shepherd's crook bending of shoot tips. Fire Blight enters through wounds and natural openings, then rides water films, insects, and contaminated tools. Wet foliage and hail or pruning injuries often precede outbreaks. Causal agent: Erwinia amylovora. In regenerative gardens, prioritize sanitation, airflow, and unbroken soil cover over calendar spraying, and intervene early when symptoms appear.
Symptoms
Blossoms turn brown and water-soaked, then wilt. Shoot tips bend into a characteristic shepherd's crook shape. Leaves turn brown to black but remain attached. Bark develops sunken, dark cankers that may ooze bacterial slime. Rapid spread in warm, wet weather. Compare several plants and note whether symptoms spread after rain, insect feeding, or wet foliage. Photograph undersides of leaves and cut stems when wilt is present to refine the diagnosis. Rule out simple drought, fertilizer burn, and herbicide drift before assuming a pathogen - abiotic injury often mimics disease.
Environmental Conditions
Humid
Prevention
Plant resistant varieties. Avoid excessive nitrogen fertilization. Prune to improve air circulation. Apply streptomycin or copper sprays during bloom. Avoid overhead irrigation during bloom. Mulch to reduce splash, clear season-end debris, and avoid working plants when wet. Design beds for airflow and diverse plantings that support beneficial insects without creating permanent humid pockets around susceptible crops.
Management
Prune infected branches at least 12 inches below visible symptoms during dry weather. Sterilize pruning tools between cuts. Apply copper sprays. Remove severely infected trees. Biological controls (Serenade) during bloom. Prefer drip irrigation, morning watering, and open spacing so leaves dry quickly. Disinfect pruners between cuts on woody plants. Use copper, sulfur, or biological products only as labeled protectants when pressure is high - they rarely reverse advanced infections alone. Destroy (do not casually compost) highly infectious debris.