Synergistic Effect of Combining Plutella xylostella Granulovirus and Bacillus thuringiensis at Sublethal Dosages on Controlling of Diamondback Moth (Lepidoptera: Plutellidae)

Compatibility of the fungus Beauveria bassiana and Trichoplusia ni SNPV against the cabbage looper Trichoplusia ni: crop plant matters

BACKGROUND

Microbial insecticides are an important weapon in insect pest management, but their use is still relatively limited. One approach for increasing their efficacy and use could be to combine different pathogens to increase pest mortality. However, little is known about whether increasing pathogen diversity will improve pest management. Here, we investigated the compatibility of two pathogens for the management of the cabbage looper, Trichoplusia ni, T. ni nucleopolyhedrovirus (TniSNPV) and the entomopathogenic fungus Beauveria bassiana, on two crops, tomato and broccoli. The pathogens were applied to individual plants using ultra low volume sprays, alone or in combination, either synchronously or asynchronously. Healthy third-instar T. ni larvae were introduced to the plants before application and collected by destructive sampling 24 h after the last pathogen application.

RESULTS

Combined applications did not result in an increase in larval mortality compared to TniSNPV alone, although mortality was generally high. B. bassiana was considerably less effective on broccoli compared to tomato. In both the combined treatments, virus-induced mortality was approximately 50% lower when applied together with the fungus, while fungus-induced mortality was not affected by the virus, even when the virus was introduced 24 h before the fungus.

CONCLUSION

While our results suggest that applying this combination of entomopathogens would not be beneficial for pest management, this study illustrates the need to consider the target crop as an important driver of the efficacy of both single and mixed pathogen applications in the field. © 2024 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Comparative genomic analysis of three geographical isolates from China reveals high genetic stability of Plutella xylostella granulovirus

In this study, the genomes of three Plutella xylostella granulovirus (PlxyGV) isolates, PlxyGV-W and PlxyGV-Wn from near Wuhan and PlxyGV-B from near Beijing, China were completely sequenced and comparatively analyzed to investigate genetic stability and diversity of PlxyGV. PlxyGV-W, PlxyGV-B and PlxyGV-Wn consist of 100,941bp, 100,972bp and 100,999bp in length with G + C compositions of 40.71–40.73%, respectively, and share nucleotide sequence identities of 99.5–99.8%. The three individual isolates contain 118 putative protein-encoding ORFs in common. PlxyGV-W, PlxyGV-B and PlxyGV-Wn have ten, nineteen and six nonsynonymous intra isolate nucleotide polymorphisms (NPs) in six, fourteen and five ORFs, respectively, including homologs of five DNA replication/late expression factors and two per os infectivity factors. There are seventeen nonsynonymous inter isolate NPs in seven ORFs between PlxyGV-W and PlxyGV-B, seventy three nonsynonymous NPs in forty seven ORFs between PlxyGV-W and PlxyGV-Wn, seventy seven nonsynonymous NPs in forty six ORFs between PlxyGV-B and PlxyGV-Wn. Alignment of the genome sequences of nine PlxyGV isolates sequenced up to date shows that the sequence homogeneity between the genomes are over 99.4%, with the exception of the genome of PlxyGV-SA from South Africa, which shares a sequence identity of 98.6–98.7% with the other ones. No events of gene gain/loss or translocations were observed. These results suggest that PlxyGV genome is fairly stable in nature. In addition, the transcription start sites and polyadenylation sites of thirteen PlxyGV-specific ORFs, conserved in all PlxyGV isolates, were identified by RACE analysis using mRNAs purified from larvae infected by PlxyGV-Wn, proving the PlxyGV-specific ORFs are all genuine genes.