SOILBORNE PATHOGENS IN A VEGETABLE DOUBLE-CROP WITH CONSERVATION TILLAGE FOLLOWING WINTER COVER CROPS

A cucumber-cucumber double-crop followed by a cucumber-snap bean doubl e-crop was grown in a system using conservation tillage in relay-cropp ing following winter cover crops. Twenty different winter covers were legumes, grasses, legume-grass mixtures, crucifers, or fallow (no cove r, resident vegetation). Population densities of Pythium spp. (primari ly P. irregulare) and Rhizoctonia solani anastomosis group (AG-4) were greater following legumes than following grasses or fallow; legume-gr ass mixtures and crucifers were intermediate. Cucumber fruit rot (indu ced primarily by R. solani AG-4) was more severe following legumes and crucifers than following grasses; legume-grass mixtures were intermed iate. In the snap bean crop following cucumber, root and hypocotyl dis eases were more severe following winter covers of legumes or fallow th an following grass or legume-grass mixtures; crucifers were intermedia te. Root-knot nematodes (Meloidogyne incognita) caused injury to the s econd vegetable crop each year in all winter cover rotations.