The effects on beneficial arthropods of the exclusion of herbicides from cereal crop edges.
The arthropod faunas of herbicide-treated (mecoprop, bromoxynil and ioxynil) and untreated headland plots of a spring wheat crop were compared in a replicated within-field experiment in England, UK, in 1988. Unsprayed headland plots had more weed species, higher weed densities, greater weed biomass and a greater percentage weed cover. They supported significantly greater densities of non-target arthropods, including the non-pest species important in the diet of insect-eating gamebird chicks and polyphagous predatory arthropods (Forficula auricularia, Agonum dorsale, Tachyporus hypnorum, T. chrysomelinus, Demetrias atricapillus and Bembidion lampros) and their prey. Within enclosures placed in treated and untreated headland plots, no differences in the pitfall catch of Pterostichus melanarius or A. dorsale (the most numerous carabids) were found. A greater proportion of the A. dorsale trapped in treated plots were female. Gut contents analysis showed that fewer cereal aphids were consumed in the treated plots. Greater numbers of eggs per carabid female were found in untreated plots.