Rose Ann McGruddy

Disruption of daily patterns of activity, physiology, or social interaction is associated with stress and reduced fitness across species. In social insects such as honey bees (Apis mellifera), circadian organisation extends to the colony level, where rhythms emerge from interactions among individual clocks, hive conditions, and environmental cues. Precision apiculture offers a mature sensor toolkit for measuring colony-level variables, and several data streams carry early-warning information about colony condition. Almost all alarms, however, are triggered against set points rather than against the daily rhythm of the signal. We review each sensor technology to establish whether its data have been, or could be, analysed with a chronobiological lens, describing the measurement principle, the achievable temporal resolution and record continuity, the rhythmic signature expected on biological grounds, and any evidence that such a signature has been reported. We then use a synthetic dataset to illustrate the workflow: in this simulated example, rhythm metrics flagged a gradually developing decline approximately three weeks before a conventional threshold alert on the same data. This lead time is a property of the simulation and awaits validation on real colonies. Wherever continuous behavioural monitoring is deployed, rhythm-based metrics may offer a route to earlier, more interpretable detection of change than set point comparisons.

Double-stranded RNA (dsRNA) biopesticides offer the potential for highly targeted pest control with minimal off-target impacts. Varroa mites (Varroa destructor) are an important pest of honey bees (Apis mellifera) that are primarily managed by synthetic pesticides. A next-generation treatment using a varroa-active dsRNA, vadescana, has been developed to target calmodulin expression in varroa. We evaluated the potential exposure of non-target species to vadescana. First, we assessed potential gene silencing effects on 39 arthropods with known genomes via bioinformatics. Three mite species, monarch butterflies (Danaus plexippus), fruit flies (Drosophila melanogaster), and European earwigs (Forficula auricularia) showed theoretical potential for off-target effects. These in silico results could be used to help inform risk assessments. Second, we conducted vadescana feeding trials on the greater wax moth (Galleria mellonella), a common beehive associate. There were no significant differences in wax moth reproduction, survival, or adult F2 wing length between vadescana-fed and control groups. Male F2 body weight was slightly but significantly lower in wax moths exposed to the highest vadescana dose, with no such effect observed in female moths. Calmodulin gene expression was unaffected in wax moths. Our hazard assessment of vadescana’s lethal and sublethal effects on wax moths indicates minimal impact following continuous dietary exposure far greater than any exposure that might be expected in the field, in line with the bioinformatics findings. This biopesticide appears highly varroa-specific and likely has fewer non-target effects than many current varroa control methods.

The cover image is based on the article RNA interference as a next‐generation control method for suppressing Varroa destructor reproduction in honey bee (Apis mellifera) hives by Rose A. McGruddy et al., https://doi.org/10.1002/ps.8193. image

Current Varroa mite management strategies rely heavily on the use of pesticides, adversely affecting honey bee health and leaving toxic residues in hive products. To explore the likelihood of RNAi technology being utilised as an alternative control method for pests like Varroa, the opinions of beekeepers on the use of this new biotechnology were obtained using a mixed-methodology approach. In-person surveys and focus groups using the Q method were conducted to discover the willingness of beekeepers to utilise Varroa-targeting RNAi treatments in their hives, and to gain feedback to inform decisions before the implementation of this new technology. Overall, the beekeepers saw potential in RNAi being used to control Varroa in their hives and were eager to have access to an alternative to pesticide treatments. Participants raised concerns about unknown long-term effects on bees and other non-target species, and the potential of an uninformed public preventing them from accessing a new Varroa treatment. While further research and discussion is needed before RNAi treatments for Varroa become commercially available, RNAi technology presents a promising, species-specific and non-toxic solution for Varroa management.

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.

The most devastating pest to honey bees ( Apis mellifera ) worldwide is the parasitic mite Varroa destructor . The development of miticide-resistant mite populations has been a major driver of colony loss in many countries. We investigated the threat Varroa poses to honey bee populations in New Zealand and tested the effectiveness of the two most popular chemical treatments used by beekeepers. Colony losses reported by New Zealand beekeepers have risen over five consecutive years from 2017 to 2021, as have the proportion of losses attributed to Varroa, with this parasite found to be the main driver of colony loss in 2021. Varroa resistance to miticide treatments flumethrin and amitraz was tested. The concentration of flumethrin required to kill 50% of the mites (LC ₅₀ ) was 156 μg/g, 13 times greater than the adjusted LC ₅₀ value of 12 μg/g observed in a trial also conducted in New Zealand in 2003, thus indicating evidence of developing mite resistance to flumethrin in New Zealand. Molecular analyses searching for mutations in the Varroa genome known to be associated with flumethrin resistance found no evidence of such mutations, suggesting that any extant resistance to flumethrin has evolved independently in New Zealand. No evidence of resistance to amitraz was found, as the LC ₅₀ value of 12 μg/g was lower than what was observed in the 2003 trial (110 μg/g). Further development of integrated pest management, such as gene-silencing RNA interference (RNAi) and selective breeding of Varroa-resistant bees, is needed to effectively manage a parasite that threatens global agriculture.

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.

Social wasps are invasive in many regions around the world. In their new communities, introduced predators such as these wasps may be beneficial as consumers of exotic pests, but they will also consume native species. Here, we examined the diet of the exotic European paper wasp (Polistes dominula) and the closely related congener, Polistes chinensis, in a region of New Zealand where they co-occur. DNA barcoding was used to analyse their diet. The diet of both wasp species was largely Lepidopteran but other orders such as Hemiptera, Diptera and Coleoptera were also represented. Our analysis showed substantial site-to-site variation in diet. The two wasps differed significantly in their prey, although these differences appear to be driven by taxa identified from a small number of DNA reads in a small number of samples. Native and introduced fauna were represented in the diets of both wasps and included important agricultural pests. Of the 92 prey taxa able to be identified to species level, 81 were identified as exotic or introduced to New Zealand. The remaining 11 were species native to New Zealand. However, our estimates suggest over 50% of the prey DNA in the wasp diet is derived from native species. These wasps are abundant in some coastal and urban habitats, where they are likely to consume pest species as well as native species of conservation importance. The ecosystem services or costs and benefits provided by these invasive species are likely to be contingent on the prey communities and habitats they occupy.