Fruit Rot, Phytophthora
Phytophthora cactorum
12 host plants
Last updated
This profile synthesizes data from multiple published sources. Expert field review is in progress.
Your apple develops firm, tan-colored rot where overhead irrigation wets the fruit, typically on lower branches. Phytophthora cactorum from irrigation water causes this soilborne fruit rot. Prevent by using low-angle drip systems or microsprinklers that don't wet fruit. Susceptibility peaks ten days before harvest, so timing matters.
Use low-angle or microsprinkler heads, placed under trees, so water does not wet fruit. Drip irrigation can also be used.
Quick Reference
Management
Most critical during fruit development and ripening when overhead irrigation is used, typically June-August in the Puget Sound region. Fruit susceptibility increases dramatically in the 10 days before harvest. Most severe when warm temperatures (65-80°F) coincide with fruit-wetting events. # Source: PNW Plant Disease Management Handbook
Fruit wetting from irrigation water for any duration (1 hour minimum); warm soil temperatures (65-80°F); saturated or near-saturated soil conditions; overhead or sprinkler irrigation that contacts fruit; late-season fruit approaching harvest (increased susceptibility 10 days pre-harvest). # Source: PNW Plant Disease Management Handbook - Fruit Rot, Phytophthora
Cultural Controls
- Use low-angle or microsprinkler heads, placed under trees, so water does not wet fruit.
- Drip irrigation can also be used.
- Reduce the length of irrigation sets.