Phytophthora Blight is caused by Phytophthora capsici, a soil-borne, fungus-like water mould. It can attack roots, crowns, stems, leaves and fruit. The organism produces swimming spores that move through saturated soil and surface water, making poorly drained areas particularly vulnerable. Plants may suddenly wilt when roots or the crown are infected, while stems develop dark, water-soaked lesions. Fruit can develop rapidly expanding, water-soaked rot, sometimes followed by conspicuous white growth. The pathogen can survive in soil for years, and warm weather combined with heavy rain or saturated soil can trigger severe outbreaks.

How to Fix It
Remove infected plants: Remove badly infected plants and fruit promptly; don't compost them.
Improve drainage: Avoid low, waterlogged areas and prevent water from pooling around plants.
Keep water from moving between plants: Runoff can carry the pathogen through the garden, so don't allow irrigation water to flow from infected areas into healthy ones.
Water at soil level: Avoid splashing soil and water onto foliage and fruit.
Rotate crops: Rotate away from susceptible crops, although long-lived spores and the pathogen's broad host range make rotation alone unreliable.
Control weeds: Some weeds can act as hosts and help maintain the pathogen.
Avoid spreading contaminated soil: Clean soil from tools, footwear and equipment before moving to unaffected areas.
Choose resistant varieties: Resistant or tolerant pepper varieties can reduce losses, although resistance is not complete.