MEASUREMENTS OF PESTICIDE SPRAY DRIFT DEPOSITION INTO FIELD BOUNDARIES AND HEDGEROWS .1. SUMMER APPLICATIONS

The drift of fluorescent tracer in water and formulated pesticide spra ys was measured at different heights and distances within 6-m-wide buf fer strips (''Conservation Headlands'') and field boundaries surroundi ng mature winter cereal fields. Spray deposits were taken from artific ial collectors. There was a diminution in deposition at the hedgerow, where a 6-m-wide buffer strip of unsprayed crop was employed between t he sprayer and the hedgerow compared to where the entire crop edge was fully sprayed. There was some evidence that a mature crop would absor b some of this spray drift, reducing deposition on the hedge flora bel ow crop level and, therefore, the nature of the buffer strip as well a s it's width were thought to be important in determining hedgerow depo sition rates. Frequency distributions of deposition along strips of he dgerow revealed that the unsprayed buffer zone also served to reduce t he peaks in drift that might occur as a result of the pitch and yaw of travelling tractor booms. The vegetational complexity of the hedge bo ttom was also shown to determine spray deposition within field boundar ies. Larvae of the cabbage white butterfly (Pieris brassicae[L.]) show ed higher mortalities when exposed to hedgerow grasses adjacent to con ventionally sprayed headlands compared to those adjacent to a Conserva tion Headland. A simple methodology for spray deposition studies is ou tlined, and implications of pesticide drift into field boundaries disc ussed.