Measurements of pesticide spray drift deposition into field boundaries and hedgerows 2. Autumn applications.

Abstract

Tractor spray applications of a pyrethroid insecticide combined with a fluorescent tracer were applied to cereal field edges on four separate occasions in the autumn. Spray drift measurements were made in field boundaries adjacent to conventionally sprayed and 6-m-wide unsprayed 'Conservation Headlands,' which act as buffer zones designed to keep the outermost edge of the crop unsprayed with certain pesticide groups. The volume of drifting spray reaching field boundaries was dependent upon wind conditions and was significantly reduced by the use of these buffer zones. Comparisons of spray drift are made with comparable experiments carried out in summer cereals (reported in an accompanying paper). In a separate experiment, high mortalities of Spodoptera littoralis Boisd larvae were recorded when they were exposed to grasses collected from hedge bottoms adjacent to conventionally sprayed headlands, and from additional spray applications made with a hand-held sprayer (used to simulate the levels of drift recorded in field trials). Larval mortalities were reduced, but still detectable, when grasses contaminated with drift adjacent to Conservation Headlands were bioassayed. In light of these findings, the current recommendation of these 6-m-wide buffer zones in cereals is discussed.