SUPPRESSION OF PHYTOPHTHORA BLIGHT IN BELL PEPPER BY A NO-TILL WHEAT COVER CROP

Four mechanisms of dispersal of propagules of Phytophthora capsici wer e investigated through modifications in cultural practices and fungici de applications in field plots of bell pepper (Capsicum annuum). Dispe rsal of soil inoculum was suppressed, and final incidence of disease w as 2.5 to 43% when stubble from a fall-sown, no-till, wheat cover crop was present. Final disease incidence was 71 to 72% and pathogen sprea d occurred within and across rows when all dispersal mechanisms were o perative in plots of pepper planted into bare soil. Final disease inci dence was 42 to 78% with black plastic mulch when a sporulating pepper fruit placed on the surface served as the source of initial inoculum. The fungicide metalaxyl applied in the irrigation system did not supp ress within-row spread of surface inoculum from a sporulating fruit on plastic, but did limit across-row spread; final disease incidence in metalaxyl-treated plots was 11.5 to 14%. Pathogen dispersal mechanisms were modified most dramatically by the no-till cropping system. Thus, simple changes in cultural practices can have dramatic effects on the development of Phytophthora epidemics. Ecologically based disease man agement strategies have the potential to reduce our reliance on agrich emicals in this and similar pathosystems.