, Volume 31, Issue 1-2, pp 51-58

Side-effects of three pesticides on the predatory mite, Phytoseiulus persimilis (Acari: Phytoseiidae)

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Side-effects of three commonly used pesticides in Iran were evaluated on an introduced strain of the predatory mite, Phytoseiulus persimilis Athias-Henriot, reared for about 10 years without exposure to any pesticides. Application of pesticides was carried out either to detached bean leaves using a Potter tower at 1 mg wet deposit per cm2 or by a hand sprayer on bean plants until run off. According to an EPPO decision making scheme, pirimiphos-methyl was found to be harmful (E = 90.8%) and heptenophos harmless (E = −3.7%) to the predatory mite in the residual initial toxicity tests. For determination of the hazard class of malathion a field test was found to be necessary (E = 59.8%). Categories of 1, 2, 3 were determined for heptenophos, malathion and primiphos-methyl, respectively, using IOBC classification. Despite being harmful, it is possible to use pirimiphos-methyl 10 days before release of P. persimilis. Investigation of the contribution of both lethal and sub-lethal effects to total impact indicated the dominance of lethality in the case of pirimiphos-methyl, while malathion acted by both mechanisms. Heptenophos did not have negative effects on fecundity of P. persimilis but rather caused a higher rate of fecundity in comparison with the control. The mortality found in the heptenophos test was not significantly different from the control.

This revised version was published online in July 2006 with corrections to the Cover Date.