Managing Apple Scab on Crabapple Trees

Rapidly declining crabapple with severe apple scab, suckers, and possible calico scale. Owner questions whether to maintain (yearly fungicide) or replace.

Apple Scab Reality

• Fungal disease: olive-green to black velvety spots, yellowing, premature leaf drop.
• Wet conditions favor infection; cool weather requires longer leaf wetness.
• Generally not fatal but ruins ornamental value by August.

Three Options

1. Do nothing: Accept summer defoliation. Sanitation (remove fallen leaves/fruit) helps.
2. Fungicide program: Spray at bud break through June (mancozeb, chlorothalonil, lime sulfur, copper, potassium bicarbonate). Must repeat yearly; protectant only—won't cure existing infection.
3. Replace with resistant cultivars: 'Snowdrift' (white flowers, orange-red persistent fruit), 'Prairiefire' (dark red flowers, red bark/fruit, 15-20 ft). Resistance ≠ immunity—wet years may still cause minor scab.

Consider state extension service evaluation before deciding.