Suppression of Phytophthora Blight in Bell Pepper by a No-Till Wheat Cover Crop

Abstract

Four mechanisms of dispersal of propagules of Phytophthora capsici were investigated through modifications in cultural practices and fungicide applications in field plots of bell pepper (Capsicum annuum). Dispersal of soil inoculum was suppressed, and final incidence of disease was 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 spread occurred within and across rows when all dispersal mechanisms were operative in plots of pepper planted into bare soil. Final disease incidence 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 suppress 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 management strategies have the potential to reduce our reliance on agrichemicals in this and similar pathosystems.

Plant species diversity for sustainable management of crop pests and diseases in agroecosystems: a review

“…The vertical dispersal of pycnidiospores from basal lesions on wheat was partially impeded by a clover understorey, which acted as a sieve (Bannon and Cooke 1998). Ristaino et al (1997) found that planting a pepper crop in stubble left over from a no-till wheat cover crop significantly reduced the dispersal of Phytophthora capsici inoculum and the subsequent occurrence Phytophthora blight disease, which was mainly attributed to a simple reduction in splash dispersal of surface inoculum to aboveground parts of the plants.…”

Tillage system effect on the epidemic of soybean brown spot

“…Therefore, soil protection with straw from a different crop could delay or inhibit infection. Ristaino et al (1997) mention the same effect for the pathosystem Phytophthora capsici-pepper. The residues of a previous crop provided an effective barrier to inoculum dispersal.…”

Cultural Practices Influencing Biological Management of Crop Diseases

“…In the presence of the stubbles from a fallow-sown, no-till wheat cover crop, the dispersal of soil inoculum of Phytophthora capsici causing Phytophthora blight of bell pepper was suppressed, resulting in considerable reduction in disease incidence. The fi nal disease incidence ranged from 2.5 to 43.0 % in no-till plots as against 71 to 72 % incidence in pepper planted in a bare fi eld, where all dispersal mechanisms operated without hindrance (Ristaino et al 1997 ) . On the other hand, the detection frequency of Phytophthora sojae infecting soybean near the soil surface was two to three times greater than that of conventional till fi elds at this depth resulting in higher incidence of damping-off disease (Workneh et al 1998 ) .…”