RNA interference as a next-generation control method for suppressing Varroa destructor reproduction in honey bee (Apis mellifera) hives.

BACKGROUND: The Varroa mite (Varroa destructor) is considered to be the greatest threat to apiculture worldwide. RNA interference (RNAi) using double-stranded RNA (dsRNA) as a gene silencing mechanism has emerged as a next-generation strategy for mite control. RESULTS: We explored the impact of a dsRNA biopesticide, named vadescana, designed to silence the calmodulin gene in Varroa, on mite fitness in mini-hives housed in a laboratory. Two dosages were tested: 2 g/L dsRNA and 8 g/L dsRNA. Vadescana appeared to have no effect on mite survival, however, mite fertility was substantially reduced. The majority of foundress mites exposed to vadescana failed to produce any offspring. No dose-dependent effect of vadescana was observed, as both the low and high doses inhibited mite reproduction equally well in the mini-hives and neither dose impacted pupal survival of the honey bee. Approximately 95% of bee pupae were alive at uncapping across all treatment groups. CONCLUSION: These findings suggest that vadescana has significant potential as an effective alternative to conventional methods for Varroa control, with broader implications for the utilization of RNAi as a next-generation tool in the management of pest species. © 2024 The Author(s). Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Gene silencing for invasive paper wasp management: Synthesized dsRNA can modify gene expression but did not affect mortality.

Invasive paper wasps such as Polistes dominula are a major pest and problem for biodiversity around the globe. Safe and highly targeted methods for the control of these and other social wasp populations are needed. We attempted to identify potentially-lethal gene targets that could be used on adult paper wasps in a gene silencing or RNA interference (RNAi) approach. Double-stranded RNA (dsRNA) was designed to target genes for which silencing has proven lethal in other insects. dsRNA was provided either orally to foragers or directly injected into the wasps. We also provided the dsRNA unprotected or protected from degradation by gut nucleases in two different forms (lipofectamine and carbon quantum dots). The effects of oral delivery of 22 different gene targets to forager wasps was evaluated. The expression of five different genes was successfully reduced following dsRNA ingestion or injection. These gene targets included the FACT complex subunit spt16 (DRE4) and RNA-binding protein fusilli (FUSILLI), both of which have been previously shown to have potential as lethal targets for pest control in other insects. However, we found no evidence of significant increases in adult wasp mortality following ingestion or injection of dsRNA for these genes when compared with control treatments in our experiments. The methods we used to protect the dsRNA from digestive degradation altered gene expression but similarly did not influence wasp mortality. Our results indicate that while many of the same gene targets can be silenced and induce mortality in other insects, dsRNA and RNAi approaches may not be useful for paper wasp control.

Nesting Ecology and Colony Survival of Two Invasive Polistes Wasps (Hymenoptera: Vespidae) in New Zealand.

We examined the abundance, nesting ecology, and colony survival of two invasive species of paper wasp, Polistes dominula Christ (Hymenoptera: Vespidae) and Polistes chinensis Pérez (Hymenoptera: Vespidae), within their invaded range in New Zealand. The more recent invader, P. dominula, exhibited a strong habitat preference, reaching the highest abundances within suburban areas with an average of 87.4 wasps per 1,000 m2. Coastal habitats were also found to be suitable environments for P. dominula, although wasp abundance in these areas was comparatively lower than suburban sites at 26.5 wasps per 1,000 m2. Although P. chinensis were observed to build more nests in coastal habitats, this was not reflected in the abundance of adult wasps in these areas. Nests of P. dominula were larger and more productive, likely a result of the multiple founding and earlier emergence of workers compared to P. chinensis. Both species exhibited significant differences in nest survival, with P. dominula observed to have a higher colony survival rate, particularly in suburban habitats where this species utilized man-made substrates as nesting sites. Neither species nested within forest sites and translocated nests of P. dominula failed to thrive within forest habitats. Findings of this research suggest that P. dominula will not pose a threat to species inhabiting forested areas. Instead, biodiversity managers should focus their efforts on suburban and coastal environments as native species in these areas will require the greatest protection.