Zucchini Blossom-End Rot: Soil Fungus Management and Crop Rotation

Why Your Zucchini Rot at the Blossom End

Yellowing, stunted zucchini fruit that rot before reaching harvest size typically indicate blossom-end rot driven by soil-borne fungi—common in beds where cucurbits repeat annually.

Immediate Treatment

1. Apply organic fungicide: Copper-based sprays (e.g., Soap Shield) or potassium bicarbonate at first sign of rot.
2. Remove affected fruit to reduce fungal load.
3. Improve drainage: Amend heavy soils with coarse sand and compost.

End-of-Season Soil Remediation

• Deep-till the bed to disrupt fungal structures
• Solarize: cover moist soil with clear UV-resistant plastic for 4-6 weeks during hottest period
• Apply beneficial microbes (Trichoderma spp.) as soil drench

Critical: Crop Rotation

Do not plant cucurbits (squash, cucumbers, melons) in the same bed for 3 years. Rotate to:

• Legumes (beans, peas) – fix nitrogen
• Brassicas (broccoli, kale) – biofumigant properties
• Alliums (onions, garlic) – antimicrobial root exudates

Preventive Cultural Practices

• Mulch with straw to prevent soil splash on fruit
• Water at base only—drip irrigation ideal
• Space plants for airflow (3-4 feet between zucchini)
• Choose resistant varieties when available

Consistent rotation and soil health building break the fungal cycle more effectively than any single treatment.