Effects of pesticides on non-target invertebrates in arable crops and field boundaries

Data are presented from experimental work carried out under two inter-related projects. The first project concerned the role of an outer unsprayed six-metres of cereal crop (`Conservation Headland') in reducing the effects of pesticide drift into field boundaries, potentially ameliorating the harmful environmental effects on beneficial arthropods. The findings showed that such strips substantially reduced drift, giving `added value' to a farm management technique already shown, because of the improved habitat it represented, to benefit populations of gamebirds, butterflies and predatory arthropods. The second part of this drift-related work was to evaluate the toxicity of the synthetic pyrethroid insecticide deltamethrin at `drift' levels to Lepidoptera larvae (Pieris brassicae and P.rapae) in the laboratory. A model predicting mortality at given levels of drift indicated high levels of short-term risk to larvae exposed to rates of drift deposition recorded in the field. The potential of buffer zones to reduce the toxicological impact of spray drift in the field is discussed. The second half of the overall programme was a project set up by the UK Ministry of Agriculture, Fisheries and Food to investigate the long-term effects of pesticide use on non-target invertebrates in arable crops. This involved monitoring the arthropod populations from three farms, in each of which fields were split into `Reduced Input Approach' (RIA) and `Current Farm Practice' (CFP) treatments. The main sampling method used was pitfall trapping. There was one `baseline' year of data collection before the treatments were established. Data from the first three treatment years of this long-term project indicated that most damage to populations of beneficial arthropods was done by autumn- and winter-applied broad-spectrum insecticides. Supporting ecological and toxicological studies were carried out to help interpret the results from the field monitoring, in particular in terms of the experimental design of the project.</p