Efficacy and persistence of insecticide residues on fruit of kiwifruit to prevent greedy scale (Hemiptera: Diaspididae) crawler settlement

Abstract

Insecticides were applied to kiwifruit (Actinidia deliciosa) in February and April 1992 and April 1993. A bioassay technique was used to measure levels of greedy scale, Hemiberlesia rapax (Comstock), crawler settlement on fruit at various times after insecticide application. Organophosphate and pyrethroid residues remaining on the fruit were measured but not the mineral oil residues. The February and April 1992 trials showed that diazinon, chlorpyrifos, and diazinon/permethrin gave shortlived protection compared to phosmet, mineral oil, and pirimiphos-methyl/permethrin. The residual times for 50% of fruit to be settled by scale in the April 1993 trial were: pirimiphos-methyl/permethrin, half rate <8 days; 1% Citrole mineral oil, 8 days; pirimiphos-methyl/permethrin, full rate 16 days; 1% Sunspray Ultra-Fine mineral oil, 19 days; 2% Citrole, 21 days; and 2% Ultra-Fine, 24 days. Estimates of residue levels at which 50% of fruit were settled by scale were generally below or similar to the maximum residue levels set by the Codex Alimentarius Commission. The potential for reducing residues at harvest is discussed. © 1995 The Royal Society of New Zealand.