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Crab Apple Fire Blight Diagnosis: Lab Confirmation Needed Without Classic Symptoms

Atypical Presentation

Branch dieback without ooze, blackening, cankers, or shepherd's crook suggests possible fire blight but not confirmed. Ooze appears only under specific humidity/temperature.

Definitive Diagnosis

Submit samples to county Agricultural Extension Service for microscopic bacterial exam. They often offer free/low-cost testing.

Meanwhile

Prune dead branches 12" below visible damage.
Sterilize tools between cuts (10% bleach or alcohol).
Avoid nitrogen fertilizer (promotes susceptible growth).

Plant Diseases: Fire Blight on Loquat: Pruning and Streptomycin Protocol; Crab Apple White Fluffy Growth: Scale or Powdery Mildew?; Crabapple Defoliation: Identify Pest Before Spraying; Fire Blight on Bradford Pear: Pruning, Disinfection, and Dormant Sprays; Fire Blight-Ravaged Pear Tree: Removal and Replanting Strategy; Rose Fire Blight Replant: Soil Treatment Myth and Copper Spray; Fire Blight on Pear and Apple: Streptomycin Spray at Bud Break; Fire Blight on Lemon Tree? Unlikely—Look for Other Causes; Diagnosing Red Mounds on Ornamental Crabapple; Fire Blight: Symptoms, Disease Cycle, and Management for Rosaceous Plants

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