Pesticide toxicity in a pyrethroid resistant strain of Phytoseiulus macropilis (Acari: Phytoseiidae)

Abstract: Phytoseiulus macropilis Banks is one of the most important predatory mites used for the control of the two-spotted spider mite in Brazil. The objective of this research was to evaluate the toxicity of pesticides of different chemical groups in a pyrethroid resistant strain of P. macropilis, under laboratory conditions. The LC50 (medium lethal concentration) values of the pyrethroids fenpropathrin, bifenthrin and deltamethrin, for the adult females of this strain of P. macropilis, were at least ten times higher than the field recommended concentrations of these compounds in Brazil. In spite of the very low toxicity of the pyrethroids to the mites of this strain, mortalities above 90% (in adult females) were observed for the recommended concentrations of acephate, abamectin, milbemectin, diafenthiuron, chlorfenapyr, fenpyroximate and etoxazole. Intermediate toxicity was verified for propargite, which caused mortality of approximately 40% in adult mites at the recommended concentration. Spiromesifen did not cause significant mortality to the eggs of the predatory mite.