SUMMARY

Toxic and sublethal effects of the biopesticide Kingbo (oxymatrine 0.2 % + psoralen 0.4%) on female adults of two-spotted spider mite (Tetranychus urticae Koch) were inves-tigated in two laboratory bioassays. The assays were set up in four replicates on bean leaf discs (30 mm in diameter) placed on moistened cotton wads in Petri dishes. Pre-ovipositional females were then released on them and treated directly with the biopesti-cide at a concentration series using a Potter device (2 ml liquid, 100 kPa air pressure, 2.7 ± 0.2 mg/cm2 aqueous deposit). Each replicate included 4-7 Petri dishes containing a total of 20-35 females. In the first assay, females were exposed to continuous acaricidal activi-ty on treated discs over a period of 96 h; in the second assay, they were exposed for 24 h and then transferred to untreated discs and kept there for the next 72 h. Kingbo toxicity to females, expressed as LC50, was significantly higher in the first bioassay (14.83 μl/l) than in the second one (26.39 μl/l). Total gross fecundity of females in the first assay was reduced by 37-95 % and net fecundity by 48-97%, depending on concentration; in the second assay, the respective fecundity reductions were 15-87 % and 23-91%. We found that a 24 h expo-sure to the biopesticide Kingbo was sufficient for sustaining significant toxic and sublethal effects. Further research should provide additional data on the recovery potential of T. urti-cae populations