Toxicity of pesticides to <i>Aphelinus mali</i> the parasitoid of woolly apple aphid

Abstract

The parasitoid Aphelinus mali controls woolly apple aphid (WAA; Eriosoma lanigerum) in New Zealand apple orchards The effects of seven pesticides on A mali exposed to residues on filter paper were assessed in a laboratory bioassay immediately postapplication Spinosad at label rate was moderately to highly toxic but other compounds and lower rates of spinosad had no detrimental effects on A mali Another bioassay incorporating field application and exposure to aged residues on leaves determined the toxicity of carbaryl diazinon indoxacarb and lime sulphur Carbaryl had the greatest residual toxicity to A mali on harvested leaves causing 85 mortality 21 days after application declining to 40 by 28 days In contrast diazinon initially caused high mortality but residues were not toxic 15 days after application while indoxyacarb and lime sulphur were not toxic Minimising the use of pesticides toxic to A mali should benefit the sustainable management of WAA in apple orchards