The effects of Kingbo biopesticide on Tetranychus urticae Koch female adults

Toxic and sublethal effects of the biopesticide Kingbo (oxymatrine 0.2% + psoralen0.4%) on female adults of two-spotted spider mite (Tetranychus urticae Koch) were investigatedin two laboratory bioassays. The assays were set up in four replicates on beanleaf discs (30 mm in diameter) placed on moistened cotton wads in Petri dishes. Preovipositionalfemales were then released on them and treated directly with the biopesticideat 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 totalof 20-35 females. In the first assay, females were exposed to continuous acaricidal activityon treated discs over a period of 96 h; in the second assay, they were exposed for 24 hand then transferred to untreated discs and kept there for the next 72 h. Kingbo toxicity tofemales, expressed as LC50, was significantly higher in the first bioassay (14.83 μl/l) than inthe second one (26.39 μl/l). Total gross fecundity of females in the first assay was reducedby 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 exposureto the biopesticide Kingbo was sufficient for sustaining significant toxic and sublethaleffects. Further research should provide additional data on the recovery potential of T. urticaepopulations