Phytophthora blight

Phytophthora blight (Phytophthora capcisi) is a highly destructive disease of peppers and cucurbits. It can become a serious problem during periods of heavy rainfall; the pathogen can spread rapidly through the crop, resulting in severe losses within a short time.

Symptoms
Leaves first show small dark green spots that enlarge and become bleached, as though scalded. If the plant stems are infected, an irreversible wilt of the foliage occurs. Infected fruits initially develop dark, water-soaked patches that become coated with white mold and spores of the fungus. Fruits wither but remain attached to the plant. Seeds will be shriveled and infested by the fungus.

Prevention
Practice crop rotation with crops other than tomato, aubergine, and cucurbits for at least 3 years. Avoid poorly drained fields for growing these crops. Plant the crop on a ridge, or better yet on raised, dome-shaped beds to provide better soil drainage. Unmulched, lowprofile beds will deteriorate during the season and may not provide sufficient drainage in July and August when disease spread can occur. Maintaining the uniform soil moisture necessary to prevent blossom end rot of peppers is difficult with raised beds unless trickle irrigation is used. Overhead irrigation, like rainfall, will encourage disease spread and should be discontinued if the disease is present. Fungicide use will vary depending upon the crop grown and in some cases the particular disease phase to be controlled. Soil fumigation, although useful in greenhouse situations, is not practical for field use because the fungus quickly reinvades treated soil.