A comparison of some important chick-food insect groups found in organic and conventionally-grown winter wheat fields in southern England.

Abstract

Fields of winter wheat on organic and conventional farms were sampled for weeds and insects in June/July in 1990 and 1991. Organic fields were paired with adjoining conventionally-managed ones and the densities of important, beneficial insect groups compared using a D-vac vacuum suction sampler. Weed counts showed greater percentage cover of broad-Ieaved weeds in organic fields than in conventional ones, with three times as many species present where herbicides were not used. Higher densities of aphids and most aphid predators were found in conventionally-grown fields. Although higher densities of the chick-food insects of farmland birds, namely weevils, leaf beetles, spiders, plant hoppers, plant bugs and sawfly larvae were found in organic fields many of these differences were not significant at the 5% level of probability. Reasons for these differences or the lack of them are discussed.