Diseases of pepper (
Phytophthora root rot
Root rot, caused by the soil borne organism Phytophthora capsici, is most severe in heavy wet soils that favor growth and spread of P. capsici. Disease usually occurs in low spots in the field and is confined to discrete areas of poor drainage (photo 1). Infected plants wilt quickly in wet soils (photo 2) and have rotted roots (photo 3). P. capsici has motile asexual spores that move in free water in the soil and infect roots; these spores also move in irrigation water. Sexual spores are produced in plant tissue and can survive in residue or in the soil for long periods of time.
Disease can be prevented by rotation from peppers for at least 3 years and by avoiding heavy soils and prolonged periods of saturated soils. In furrow irrigated peppers, disease can be reduced by cultural practices that increase drainage and reduce the chance of over watering in furrow irrigation, such as laser leveling, irrigation of alternate rows, shorter rows, cultivation to keep plants high on the bed, and shorter irrigations. In center pivot, the field should be properly leveled to remove low spots. Chemical control is effective for disease prevention. Metalaxyl is registered and will prevent new infections but will not cure plants that are already diseased.
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February 24, 2003