The Effects of Kingbo Biopesticide on Tetranychus urticae Koch Female Adults

Abstract

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 investigated 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. Preovipositional females were then released on them and treated directly with the biopesticide 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 activity 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 exposure 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. urticae populations.

Toksični i subletalni efekti biopesticida Kingbo (oksimatrin 0,2% + psoralen 0,4%) na odrasle ženke obične paučinaste grinje (Tetranychus urticae Koch) ispitivani su u dva laboratorijska ogleda. Ogledi su izvedeni u četiri ponavljanja na kružnim lisnim isečcima primarnih listova pasulja (prečnika 30 mm) postavljenim u petri-sudove na navlaženu vatu, na kojima su pre-ovipozicione ženke direktno tretirane serijom koncentracija biopesticida pomoću Poter-aparata (2 ml tečnosti, pritisak 100 kPa, vlažni depozit 2,7 ± 0.2 mg/cm2). Tretirano je 4-7 petri-sudova sa 20-35 ženki po ponavljanju. U prvom ogledu ženke su bile 96 h kontinuirano izložene delovanju akaricida na tretiranim isečcima, dok su u drugom ogledu posle 24 h prebačene na netretirane isečke, gde su ostale naredna 72 h. Na nivou LC50, utvrđena je značajno veća toksičnost biopesticida Kingbo za ženke u prvom ogledu (14.83 μl/l) u poređenju sa ženkama u drugom ogledu (26.39 μl/l). Ukupan bruto-fekunditet ženki u prvom ogledu redukovan je za 37-95%, a neto-fekunditet za 48-97%, u zavisnosti od koncentracije; u drugom ogledu odgovarajuća redukcija fekunditeta iznosila je 15-87% i 23-91%. Konstatovano je da je 24-časovna ekspozicija biopesticidu Kingbo dovoljna za nastajanje značajnih toksičnih i subletalnih efekata, kao i da su potrebna dalja istraživanja u cilju preciznije procene potencijala oporavka populacije T. urticae.