Bnk. Davis et al., THE EFFECTS OF HEDGES ON SPRAY DEPOSITION AND ON THE BIOLOGICAL IMPACT OF PESTICIDE SPRAY DRIFT, Ecotoxicology and environmental safety, 27(3), 1994, pp. 281-293
Two series of drift deposition measurements were carried out at differ
ent wind speeds using sodium fluorescein as a tracer dye sprayed over
a grass field 6 m upwind of a hedge. Efficient receptors were placed b
elow and above hedge height (1.6 m) between 1 and 20 m downwind from t
he sprayed area. Receptors below hedge height reflected a sudden decre
ase in deposition immediately behind the hedge, followed by a gradual
increase again up to 15 m, i.e., nine times the height of the hedge. T
he sheltering effect of a hedge from the biological impact of spray dr
ift was studied by bioassays using tomato and Lychnis flos-cuculi plan
ts for the herbicide MCPA and young Pieris brassicae larvae for the in
secticide cypermethrin. These demonstrated that the protection afforde
d to sensitive species in strong winds may be quite limited, and sever
e damage may be inflicted over considerable distances. In intermediate
cases, a protected zone is followed by a zone of further significant
damage before drift depositions cease to have further effect. In some
cases, the sheltered zone may extend to a distance where drift deposit
ion, even in the absence of a hedge, has minimal effect. (C) 1994 Acad
emic Press, Inc.