Loss of residual activity of abamectin on foliage against adult hymenopteran parasitoids

The residual activity of abamectin against adult maleCotesia plutellae Kurdj. (Hym.:Braconidae) appeared to be markedly less on freshly sprayed Chinese cabbage (Brassica chinensis var. pekinensis cv Up Top) leaves compared with residues on glass. The residual activity of abamectin against adult maleDiadegma semiclausum Hellén (Hym.:Ichneumonidae) was also shown to decline rapidly on Chinese cabbage with no detectable activity remaining two days after spraying with concentrations in excess of the recommended field rates. The residual activity of abamectin against both species appeared to be consistently greater on Chinese cabbage compared with common cabbage (B. oleracea var. capitata cv Wheeler’s Imperial).