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pp.47-58
, , Effect of a new crop protectant ‘Bt-Plus’ on natural enemies was analyzed in this study. Tested natural enemies included two parasitic species of Aphidius colemani and Eretmocerus eremicus, and four predatory species of Harmonia axyridis, Orius laevigatus, Amblyseius swirskii, and Phytoseiulus persimilis. ‘Bt-Plus’ was formulated by combination of three entomopathogenic bacteria (Xenorhabdus nematophila (Xn), Photorhabdus temperata subsp. temperata (Ptt), Bacillus thuringiensis (Bt)) and bacterial metabolite (BM). All three types of ‘Bt-Plus’ showed significantly higher toxicities against fourth instar Plutella xylostella larvae than Bt single treatment. Two types of bacterial mixtures (‘Xn+Bt’ and ‘Ptt+Bt’) showed little toxicity to all natural enemies in both contact and oral feeding assays. However, ‘BM+Bt’ showed significant toxicities especially to two predatory mites of A. swirskii and P. persimilis. The acaricidal effects of different bacterial metabolites were evaluated against two spotted spider mite, Tetranychus urticae. All six BM chemicals showed significant acaricidal effects. The BM mixture used to prepare ‘Bt-Plus’ showed a high acaricidal activity with a median lethal concentration at 218.7 ppm (95% confidence interval: 163.2 - 262.3). These toxic effects of bacterial metabolites were also proved by cytotoxicity test against Sf9 cells. Especially, benzylideneacetone, which was used as a main ingredient of ‘BM+Bt’, showed high cytotoxicity at its low micromolar concentration.
