Apple Scab Management in Crabapple Trees

Crabapples losing leaves annually right after blooming are infected with apple scab (Venturia inaequalis) — a fungal disease requiring precisely timed preventive treatment.

Critical Treatment Window

Fungicide applications must begin at bud break (when leaf tips emerge) and continue every 7-14 days through petal fall. Spraying after symptoms appear (summer) is ineffective — the infection occurred weeks earlier.

Recommended Fungicides

• Myclobutanil (Immunox)
• Propiconazole (Banner Maxx)
• Chlorothalonil (Daconil)
• Captan

Rotate chemistries to prevent resistance.

Cultural Practices for Long-term Health

• Fall fertilization: Low-nitrogen formula to strengthen for next season.
• Spring pruning: Thin canopy for air circulation and faster leaf drying.
• Sanitation: Remove and destroy all fallen leaves — they harbor overwintering spores.
• Resistant cultivars: When replacing, choose scab-resistant varieties (e.g., 'Prairifire', 'Adirondack', 'Sugar Tyme').

With consistent early-season fungicide programs and cultural management, crabapples retain foliage through summer and build reserves for better flowering.