The influence of weeds on polyphagous arthropod predators in winter wheat

Abstract In 1980 and 1981, pitfall traps and an insect vacuum net were used to sample polyphagous predators in plots of winter wheat treated or not treated with herbicides. Dense populations of broad-leaved and grass weeds occurred in untreated plots. Significantly more large carabids ( Pterostichus melanarius and P. madidus ) were caught in pitfall traps in treated than in untreated plots, where their activity may have been reduced by the vegetation. Numbers of the carabids Loricera pilicornis, Agonum dorsale and Amara species, of the staphylinids Philonthus cognatus, Tachinus signatus, Tachyporus species and Aleocharinae and of larvae of both families were significantly reduced by herbicide treatments. Some species were unaffected by the treatments. Cereal aphids were sparse during the trials and their numbers were unaffected by herbicide treatments. In 1981, more Sitobion avenae occurred on the cultivar Maris Huntsman than on Kador.