Metabolic resistance mechanisms of Laodelphax striatella to several insecticides, such as neonicotinoids, organophosphates and pyrethroids, have been investigated by evaluating the transcription levels of CYP450 genes. Nevertheless, no study on the CYP450-mediated carbamate resistance in L. striatella has been conducted to date. Here, we determined the transcription levels of six CYP450 genes and one carboxylesterase gene to screen detoxification genes associated with carbamate resistance. The CYP6CW1 exhibited the highest transcription level (18 fold) in a resistance strain. Interestingly, its transcription level increased slightly (3 fold) in a susceptible strain upon the exposure to a sublethal dose (LC30) of carbofuran. These results suggest that CYP6CW1 expression is inducible by carbofuran and its overexpression is likely responsible for carbofuran tolerance and resistance in L. striatella.

Diamondback moth (Plutella xylostella L.) belonging to genus Lepidoptera is a notorious pest of cruciferous crops worldwide. We evaluated the bioinsecticidal activity of the liquid cultures (LB and NB) of a bacterial strain, Serratia sp. EML-SE1, isolated from a diseased diamondback moth. The pathogenicity of a bacterial strain to diamondback moth was confirmed by the following procedures: treatment of liquid culture on cabbage leaves, ingestion of inoculated cabbage and mortality response. For the test, twenty 3rd instar larvae of diamondback moth were placed on the Chinese cabbage leaf in a round plastic cage (Ø 10 × 6 cm) and sprayed with the liquid cultures. After 72 hours, insecticidal activity of LB and NB cultures of Serratia sp. against P. xylostella larvae showed 91.7% and 88.3%, respectively. In addition, the bioinsecticidal activity on potted cabbage with 14 leaves in a growth cage (165 × 83 × 124 cm) also was similar to that of plastic cage experiment. Summarized, the Serratia sp. EML-SE1 may be a potent candidate as a bioinsecticidal agent to control diamondbac kmoth.