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.

Two species of entomogenous fungi were discovered infecting the invasive paper wasp Polistes chinensis during an ecological study on Farewell Spit, New Zealand. We sequenced two nuclear ribosomal RDNA genes, the internal transcribed spacer (ITS) and the small ribosomal subunit 18S, and one protein-coding gene, the translation elongation factor 1-alpha (ef1 α). Combining sequence information with morphological examination, we identified these species as Beauveria malawiensis and Ophiocordyceps humbertii. We estimated that these fungi produce infection in approximately 3.3% of colonies in our study population. In bioassays, we successfully infected P. chinensis individuals from healthy colonies with B. malawiensis, with significant effects on adult mortality. This is the first record of both B. malawiensis and O. humbertii from Polistine hosts in New Zealand, and the first investigation into disease causality by these pathogens in P. chinensis. Our findings may contribute to the future development of biological control agents for paper wasps in New Zealand and elsewhere around the world.

Studying the efficacy of control methods is paramount to successful management of invasive pests and understanding why some colonies survive is important to improve management practices. Here, the bait Vespex® was used to control invasive wasps across 64 ha of forest in an invaded range near Hanmer Springs, New Zealand. Bait was applied across a standard 50 m by 300 m arrangement and made available for 3 days. Nest mortality rates after 19 days were 29.8%, although nearly all nests were affected with a median overall reduction in nest traffic of 96.5%. The results from logistic regression showed that, all else remaining equal, larger wasp nests, nests further from bait stations, and more isolated nests exhibited lower rates of mortality after baiting. Investigating the change in activity at surviving nests, the results from beta regression suggest that declines in nest traffic were less severe with increasing distance to the nearest bait, but more severe with increasing nest size. These results indicate that while smaller nests are at a higher risk of being killed by the bait, they may not encounter bait as regularly as larger nests. Bait uptake varied considerably across bait stations. Wasp nests were not randomly or uniformly distributed in space, and instead were aggregated across our treatment area, likely due to some aspects of environmental conditions. We suggest further research to be focused on developing an understanding of the drivers of wasp nest development and foraging behaviour, to produce a more flexible baiting procedure that will increase both baiting efficiency and efficacy.

The Asian paper wasp (Polistes chinensis) is an invasive species in New Zealand and a voracious arthropod predator, incorporating a wide range of prey into its diet. We examined the colony survival and prey community composition of these wasps in a protected coastal habitat in New Zealand. Paper wasp colonies at this site were surveyed and monitored weekly over two summers. Our data showed that only ~20% of the monitored colonies each year survived until late summer, with high rates of colony mortality in late spring and early summer. We collected samples of wasp larval guts over a temporal gradient in one nesting season, and via DNA metabarcoding analysis, we identified the prey species consumed. The prey species most frequently identified in larval samples were endemic cicadas and several lepidopteran species. No native arthropod species of known conservation concern were identified in the analysis. However, 63% of the unique taxon sequences retrieved could not be identified by genus or species level, likely due to the absence of reference barcodes. These taxa may represent a group of understudied species, potentially highly endemic or localised. Our analysis indicates that these invasive wasps are opportunistic‐generalist predators with the potential to exert high predation pressure on native arthropods. P. chinensis may be preying on a range of understudied species, especially in remote, natural habitats across New Zealand. We recommend future studies continue to barcode native New Zealand arthropods in order to improve the taxonomic assignments of dietary studies.