The effects of intensive farming on some beneficial insect species.

Abstract

The effects of modern intensive agriculture on two groups of beneficial insects were studied from 1976 to 1982 on farmland in southern England. The first group of such insects was represented by the leaf-beetle, Gastrophysa polygoni (L.) (Coleoptera : Chrysomelidae) . This species lives in cereal fields feeding upon weeds of the genus Polygonum e.g. knotgrass (Polygonum aviculare L.) and black bindweed (Polygonum convolvulus L.} . Weed-dwelling insect species especially G. polygoni have been shown in some years to constitute a numerically inrportant component of the diet of grey partridge chicks (Perdix perdix) (1). The decline of the grey partridge since the 1940's can be explained in terms of decreased chick survival which can, in turn, be linked to changes in the abundance of their insect food in cereal crops (2). Changes in the quantity of such insect food have been considered to be caused by a range of agricultural practices (3 & 4). In this study, the effects of several agricultural practices on G. polygoni were investigated in the field and laboratory.