A method for laboratory test of side-effects of pesticides on Leptomastix dactylopii (How.) Hym. Encyrtidae).
A method is described of using the parasite Leptomastix dactylopii How. reared on its natural host Planococcus citri (Risso) on potato sprouts by the method of G. Viggiana [see RAE/A 64, 6905] as a test insect for the laboratory assessment of the side-effects on beneficial insects of insecticides applied against pests. Glass plates are sprayed with the test chemical at 0.5 g suspension or emulsion/100 cm2, dried, and then assembled into sets of glass boxes connected by tubing to a forced-ventilation apparatus and containing adult parasites, hosts and a pad soaked in honey and water for adult nutrition. Premature death of the adults is observed within the boxes, and the number of parasitised hosts and the survival and development of the new generation of parasites are observed after transfer of the hosts (after 24 h) into a pesticide-free environment; these are compared with the corresponding rates observed for untreated hosts and parasites, and the 'reduction of beneficial capacity' caused by the chemicals is assessed. Chemicals were considered harmless to the parasites if less than 50% reduction occurred, slightly harmful at 50-79% reduction, moderately harmful at 80-90% reduction and harmful at over 99% reduction of beneficial capacity. According to this test method, temephos (Abate), ethiofencarb, methomyl and Decis [(S)-cyano(3-phenoxyphenyl)methyl (1R-cis)-3-(2,2-dibromoethenyl)-2,2-dimethylcyclopropanecarboxylate] were harmful and fenbutatin oxide (Torque) was harmless to the parasite.