Phosmet was applied in mid season to #x201C;T-bar#x201D; trellised kiwifruit (Actinidia deliciosa) by airblast sprayer at 112.5 g a.i/100 litres and 2250 litres/ha. Residue levels on the upper and lower surfaces of leaves from two canopy zones and two shoot types were assessed by chemical and biological assays. Chemical assays used a brief solvent wash of a fixed area of the separate leaf surfaces. In the bioassays neonateEpiphyas postvittana(Walker) larvae were cagedon each surface. These procedures were repeated 1, 3, 8, 14, and 29 days after spray application in mid summer. Mean initial residues ranged from 2.1 #x3BC;g/cm2to 9.0 #x3BC;g/cm2, with levels 2#x2013;3 times greater on lower surfaces than upper surfaces. Residue half-lives calculated for lower leaf surfaces ranged from 6 to 20 days. The half-life for upper surface residues was estimated graphically at 3 days. Differences in the initial residue levels between canopy zones and shoot types tended to be offset by subsequent decay rates. Chemical assays and mortality results with progressively aged residues were used to estimate the decay period required for residue efficacy against lightbrown apple moth to decline to 70 24 h mortality. This ranged from 21 to more than 29 days on lower leaf surfaces.
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