Pepper plants can be vulnerable to fungus in wet conditions, whether this involves hot and humid weather in the 90s or a series of overcast, drizzly days in the 60s. Unattractive fuzzy spots on leaves or fruit or collapsing foliage may indicate the arrival of unwelcome spore-producing organisms. Pepper fungus indicates a potentially serious threat to your crop harvest and requires mitigation.
A rapid collapse and death may indicate Fusarium wilt or Verticillium wilt, caused by fungi of the same name. Large circular or oblong spots on leaves and stems may indicate cercospora leaf spot, caused by Cercospora capsici. Plants that suddenly turn yellow and brown may have Southern blight, caused by Sclerotium rolfsii. Root rot, stem canker, leaf blight and fruit rot may indicate Phytophthora blight, caused by Phytophtora capsici. Affected areas may have a white mold border. Circular sunken spots on ripe fruit may indicate anthracnose, or ripe pepper disease, due to Colletotrichum piperatum growth. Dusty black spores near sunscalds or puncture wounds indicate alternaria rot, caused by Alternaria solani.
Southern blight is more prevalent in southeastern and Gulf Coast areas of the United States, given that temperatures above 86 degrees Fahrenheit favor its development. Verticillium wilt is more common in the western and northern parts of North America, according to Texas A&M. Fusarium wilt occurs in regions with a combination of wet soil and high temperatures.
Plant peppers in well-drained soil to mitigate the effect excessive dampness has on fungal diseases. Avoid planting peppers in low-lying areas and create raised beds to allow moisture to drain away from the base of the plant after rain. Commercial growers need to provide drainage at the bottom of fields to allow excess water to flow out, recommends Thomas A. Zitter, a plant pathologist at Cornell University.
A crop rotation of four to six years is needed to reduce populations of wilt fungi. Plant cereals and grasses where possible and avoid planting members of the solanaceous family, which includes potatoes, tomatoes and eggplants as well as peppers.
During the growing season, control fungal infections with copper fungicide, beginning at the first stage of the disease and continuing at one- to two-week intervals, states Texas A&M AgriLife Extension. Remove and destroy infected plants after harvest, advises the Ohio State University Extension.