Title

Phytophthora blight of pepper (Phytophthora capsici Leonian) and its integrated disease management

Date of Completion

January 2004

Keywords

Agriculture, Agronomy|Agriculture, Plant Pathology

Degree

Ph.D.

Abstract

Pepper (Capsicum annuum L.) is an important high value crop grown for vegetable and for spice purposes. Phytophthora blight caused by Phytophthora capsici Leonian is a serious disease of pepper. The objective of the study was to determine effective control measures for integrated management of Phytophthora blight, which might reduce chemical fungicides use. Studies were carried out under greenhouse/screenhouse conditions to determine: races, mating types and metalaxyl sensitivity, survival of P. capsici in run-off, pond water contamination, and effects of some environmentally safe measures to reduce Phytophthora blight. In 2002/2003, pepper genotypes were screened for resistance under laboratory and field conditions at the University of Connecticut and in Nepal respectively. In 2003, 8/9 different disease control treatments were evaluated in farmers' fields in two locations in Nepal. Results showed: existence of races, most of the isolates sensitive to metalaxyl (Krilaxyl), and out of 85, 83 isolates A1 mating type. One irrigation pond at Somers, Connecticut was found contaminated in September 2002. Colony forming units recovery declined significantly over time. Under greenhouse/screenhouse conditions significant reduction in disease incidence was observed in mustard meal amended soil, and in 7 and 8-week-old seedlings compared to younger seedlings. PlantShield (Trichoderma harzianum) and SoilGard ( Gliocladium virens) were found effective compared to control. Most of the genotypes were moderately susceptible to susceptible under laboratory conditions. Field study showed 7 genotypes resistant, 9 moderately resistant, 15 moderately susceptible and 9 were susceptible. Among the treatments evaluated, three reduced Phytophthora blight significantly: seedling treatment followed by two foliar sprays with Dhanucop (50% copper oxychloride) or Krilaxyl (8% metalaxyl + 64% mancozeb) and seedling treatment with Krilaxyl in combination with G. virens application in the planting hole. To confirm mustard meal and chicken manure effects in the field requires more research. Based on overall results it is concluded that monitoring of irrigation pond water, use of 7- and 8-week-old seedlings, and treatment with Dhanucop or Krilaxyl alone or in combination with G. virens can be helpful for integrated management of Phytophthora blight. Resistant or moderately resistant genotypes could be the base for developing resistant genotypes with better horticultural traits. ^