Effect of apple orchard floor vegetation on density and dispersal of phytophagous and predaceous mites in Utah

Abstract

Studies were conducted in four northern Utah apple orchards in 1990 and 1991 to determine the influence of orchard ground cover composition on density and dispersal of phytophagous and predaceous mites. The dispersal of phytophagous mites from ground cover plants into trees was enhanced by the presence of seven broadleaf weeds (common mallow, field bindweed, knotweed, morning glory, prickly lettuce, puncture vine, and white sweet-clover) and apple root suckers that served as reproductive hosts for the mites (i.e. spider mite egges, immatures, and adults were observe). Orchards with a total ground vegetation cover of 50% or more and less than 12% cover of reproductive host plants for mites had adequate predaceous mite populations to maintain phytophagous mite densities in trees below economically damaging levels.