• Korean journal of applied entomology
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• v.51 no.3
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• pp.245-253
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• 2012

Benzylinedeneacetone (BZA) is a bacterial metabolite which is synthesized by at least two entomopathogenic bacteria, namely Xenorhabdus nematophila and Photorhabdus temperata subsp. temperata. It has been shown to possess inhibitory effects on insect cellular and humoral immune responses as well as antimicrobial activities against various species of bacteria and fungi. However, its relatively high phytotoxicity, and nonsystematic effect have thus far prevented its development into an optimal pesticide. This study screened five different BZA derivatives in order to select an optimal compound, which would have relatively high solubility and low phytotoxicity while retaining sufficient degrees of the immunosuppressive and antimicrobial activities associated with BZA. Hydroxylation of the benzene ring of BZA was found to significantly suppress its immunosuppressive and antimicrobial activities. Transformation of the ketone of BZA by carboxylation also suppressed the inhibitory activities. However, a shortening of the aliphatic chain of BZA into acetate form (4-hydroxyphenylacetic acid: HPA) did not decrease the inhibitory activity. HPA also showed much less phytotoxicity against the hot pepper plant Capsicum annuum, when compared to BZA. This study identified an optimal BZA derivative, which exhibited relatively little phytotoxicity, but retained a high degree of inhibitory activity to suppress insect immune responses and antimicrobial activities against plant pathogens.

• Korean journal of applied entomology
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• v.62 no.4
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• pp.277-285
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• 2023

The onion moth, Acrolepiopsis sapporensis, was monitored in the farms cultivating the welsh onion, Allium fistulosum, using sex pheromone from transplantation to harvest. Two occurrence peaks were observed at early June and late July after the overwintering population. However, the population sizes were varied among different years and the cultivating environments. To effectively control A. sapporensis with microbial pesticides, different Bacillus thuringiensis strains were screened to select B. thuringiensis kurstaki (BtK). To enhance the insecticidal virulence of BtK, the culture broth of Photorhabdus temperata temperata (Ptt) was added to the BtK. This mixture of two entomopathogenic bacteria was called 'BtPlus', which was superior to BtK alone in the insecticidal virulence. The enhanced virulence was explained by the immunosuppressive activity of the secondary metabolites contained in the Ptt extract. The metabolites inhibited both cellular and humoral immune responses of A. sapporensis, resulting in the enhanced virulence of BtK. These results suggest that A. sapporensis occurs in the welsh onion fields and the resulting economic damage would be effectively prevented by BtPlus application.

• Korean journal of applied entomology
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• v.51 no.1
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• pp.47-58
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• 2012

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.