Measurements of pesticide spray drift deposition into field boundaries and hedgerows I. Summer applications.

Abstract

The drift of fluorescent tracer in water and formulated pesticide sprays was measured at different heights and distances within 6-m-wide buffer strips ('Conservation Headlands') and field boundaries surrounding mature winter cereal fields. Spray deposits were taken from artificial collectors. There was a diminution in deposition at the hedgerow, where a 6-m-wide buffer strip of unsprayed crop was employed between the sprayer and the hedgerow compared to where the entire crop edge was fully sprayed. There was some evidence that a mature crop would absorb some of this spray drift, reducing deposition on the hedge flora below crop level and, therefore, the nature of the buffer strip as well as it's width were thought to be important in determining hedgerow deposition rates. Frequency distributions of deposition along strips of hedgerow revealed that the unsprayed buffer zone also served to reduce the peaks in drift that might occur as a result of the pitch and yaw of travelling tractor booms. The vegetational complexity of the hedge bottom was also shown to determine spray deposition within field boundaries. Larvae of the cabbage white butterfly (Pieris brassicae [L.]) showed higher mortalities when exposed to hedgerow grasses adjacent to conventionally sprayed headlands compared to those adjacent to a Conservation Headland. A simple methodology for spray deposition studies is outlined, and implications of pesticide drift into field boundaries discussed.