A comparison of the toxic and sub-lethal effects of fluvalinate and esfenvalerate on the two-spotted spider mite (Acari:Tetranychidae).
There was no difference in the direct toxicity of fluvalinate and esfenvalerate to two-spotted spider mite (TSSM), Tetranychus urticae Koch, adults. The residual toxicity LC50 of esfenvalerate was lower. Neither pyrethroid was toxic (<10% mortality) to TSSM eggs or adults at their recommended field concentrations. Fluvalinate was twice as toxic (45% mortality) than esfenvalerate to TSSM larvae at 0.01 g.a.i L-1. The toxicity of the pyrethroids to TSSM protonymphs and deutonymphs was similar (16-28% mortality at 0.1 g a.i. L-1). Dispersal from the treated surface was the main response to both pyrethroids by TSSM protonymphs, deutonymphs and adults. Maximum run-off by TSSM adults from fluvalinate and esfenvalerate treated surfaces was found with 0.01 and 0.005 g a.i. L-1 respectively. Spin-down from pyrethroid treated surfaces was positively correlated with concentration. Oviposition was negatively correlated with concentration. Fluvalinate caused greater reductions in oviposition than esfenvalerate. Both pyrethroids reduced TSSM development rate from larval, protonymph and deutonymph stages, but fluvalinate caused larger reductions. Both pyrethroids prevented mating; for ten days oviposition 93% and 98% of offspring were male for esfenvalerate and fluvalinate respectively at 0.1 g a.i. L-1. These findings are discussed with respect to the incidence of pyrethroid induced mite outbreaks.