Combined effect of Photorhabdus luminescens and Bacillus thuringiensis subsp. aizawai on Plutella xylostella.

ABSTRACT

In this study, we evaluated a new biopesticide containing different combinations of Photorhabdus luminescens (ATCC 29,999; Pl) and Bacillus thuringiensis subsp. aizawai (Bt) to leverage their insecticidal activity against Plutella xylostella. Mixtures containing proteins of various sizes were assayed to determine which combination of the two bacteria would yield the maximum insecticidal activity. A histopathologic slide revealed vacuole formations and rifts near the apical membrane (a symptom of Bt) and severe thinning of the intestinal wall (a symptom of Pl). When the two bacteria were cultured separately and then mixed, the insecticidal activity of the treatment reached 83.33% ± 8.82%. The insecticidal activity was elevated and significantly accelerated when Bt was mixed with both the Pl supernatant and the isolated protein with a molecular mass [Formula see text] 100 kDa of Pl. These results highlight the potential of Pl as a potent bioinsecticide to economically and sustainably control Pl. xylostella and other lepidopteran pests. KEY POINTS • Growth inhibition by Bacillus thuringiensis exerted a significant effect on insecticidal activity. • Large Photorhabdus luminescens proteins can accelerate the synergistic insecticidal effect on Plutella xylostella.