All together now: Geographically coordinated miticide treatment benefits honey bee health

Deformed wing virus (DWV) is a pathogenic virus of honey bees transmitted by the ectoparasitic mite Varroa destructor. Annual overwintering colony losses, accounting for ~25% of all colonies, are associated with high levels of Varroa-DWV infestation. Effective miticide treatments are available to control Varroa. However, the absence of coordinated treatment means environmental transmission of mites continues unchecked. We aimed to determine whether rational, coordinated treatment is beneficial, and characterized the DWV population as an indicator of colony health.This study uses coordinated treatment of Varroa in a geographically isolated environment (Isle of Arran, Scotland) over 3 years. The study area contained 50-84 colonies managed by ~20 amateur beekeepers. Sampling and virus analysis to assess strain diversity and viral loads were conducted before and after treatments, and changes in population diversity were quantified by sequence analysis.Over the 3 years analysis of the virus population revealed that the dominant DWV variant shifted from Type A to Type B in all apiaries, regardless of mite levels or proximity to other colonies. During this period the number of managed colonies increased by 47% (57-84 colonies), but despite this, we estimate total mite numbers decreased by 58%. Synthesis and applications. In this study, the beekeepers in Arran significantly improved the number of colonies they managed, without importing any bees onto the island, indicating that an improved focus on management techniques, through the combination of a coordinated miticide programme and an improved understanding of bee diseases, could yield positive results for bee health and sustainability.

Grand challenges in entomology: Priorities for action in the coming decades

Entomology is key to understanding terrestrial and freshwater ecosystems at a time of unprecedented anthropogenic environmental change and offers substantial untapped potential to benefit humanity in a variety of ways, from improving agricultural practices to managing vector-borne diseases and inspiring technological advances.We identified high priority challenges for entomology using an inclusive, open, and democratic four-stage prioritisation approach, conducted among the membership and affiliates (hereafter 'members') of the UK-based Royal Entomological Society (RES).A list of 710 challenges was gathered from 189 RES members. Thematic analysis was used to group suggestions, followed by an online vote to determine initial priorities, which were subsequently ranked during an online workshop involving 37 participants.The outcome was a set of 61 priority challenges within four groupings of related themes: (i) 'Fundamental Research' (themes: Taxonomy, 'Blue Skies' [defined as research ideas without immediate practical application], Methods and Techniques); (ii) 'Anthropogenic Impacts and Conservation' (themes: Anthropogenic Impacts, Conservation Options); (iii) 'Uses, Ecosystem Services and Disservices' (themes: Ecosystem Benefits, Technology and Resources [use of insects as a resource, or as inspiration], Pests); (iv) 'Collaboration, Engagement and Training' (themes: Knowledge Access, Training and Collaboration, Societal Engagement).Priority challenges encompass research questions, funding objectives, new technologies, and priorities for outreach and engagement. Examples include training taxonomists, establishing a global network of insect monitoring sites, understanding the extent of insect declines, exploring roles of cultivated insects in food supply chains, and connecting professional with amateur entomologists. Responses to different challenges could be led by amateur and professional entomologists, at all career stages.Overall, the challenges provide a diverse array of options to inspire and initiate entomological activities and reveal the potential of entomology to contribute to addressing global challenges related to human health and well-being, and environmental change.

'Candidatus Liberibacter solanacearum' distribution and diversity in Scotland and the characterisation of novel haplotypes from Craspedolepta spp. (Psyllidae: Aphalaridae)

The phloem limited bacterium 'Candidatus Liberibacter solanacearum' (Lso) is associated with disease in Solanaceous and Apiaceous crops. This bacterium has previously been found in the UK in Trioza anthrisci, but its impact on UK crops is unknown. Psyllid and Lso diversity and distribution among fields across the major carrot growing areas of Scotland were assessed using real-time PCR and DNA barcoding techniques. Four Lso haplotypes were found: C, U, and two novel haplotypes. Lso haplotype C was also found in a small percentage of asymptomatic carrot plants (9.34%, n = 139) from a field in Milnathort where known vectors of this haplotype were not found. This is the first report of Lso in cultivated carrot growing in the UK and raises concern for the carrot and potato growing industry regarding the potential spread of new and existing Lso haplotypes into crops. Trioza anthrisci was found present only in sites in Elgin, Moray with 100% of individuals harbouring Lso haplotype C. Lso haplotype U was found at all sites infecting Trioza urticae and at some sites infecting Urtica dioica with 77.55% and 24.37% average infection, respectively. The two novel haplotypes were found in Craspedolepta nebulosa and Craspedolepta subpunctata and named Cras1 and Cras2. This is the first report of Lso in psyllids from the Aphalaridae. These new haplotypes were most closely related to Lso haplotype H recently found in carrot and parsnip. Lso was also detected in several weed plants surrounding carrot and parsnip fields. These included two Apiaceous species Aegropodium podagraria (hap undetermined) and Anthriscus sylvestris (hap C); one Gallium sp. (Rubiaceae) (hap undetermined); and Chenopodium album (Amaranthaceae) (hap undetermined).

Healthy Honey Bees – analysis of the Deformed Wing Virus population to assess rational Varroa control on a Scottish island

Varroa destructor is an ectoparasitic mite associated with significant losses of honey bee colonies globally. The mite vectors a range of pathogenic viruses, most important of which is Deformed Wing Virus (DWV, (+)ssRNA). Overwintering colony losses, accounting for the death of ∼25% of all colonies each year, are associated with high levels of Varroa-DWV infestation. Effective miticide treatments are available to control Varroa. However, the absence of coordinated treatment means environmental transmission of mites continued unchecked. We aim to determine whether rational, coordinated treatment is beneficial, using features of the DWV population as an indicator of colony health. This study uses coordinated treatment of Varroa in a geographically isolated environment (Isle of Arran, Scotland). It is reported that a high level of a near-clonal virus population is associated with Varroa infestation and colony losses, whereas Varroa-free healthy colonies carry only low levels of a diverse population of DWV. The study area contains 50-85 colonies and 25 beekeepers. Sampling and virus analysis – strain diversity and viral loads – have been conducted before and after treatment. Changes in virus diversity are quantified by next generation sequencing analysis to determine population diversity. In the first two years we have observed a geographic decrease in Varroa and changes in the composition of the virus population. This study will inform our development of rational Varroa control strategies for beekeepers in temperate regions and could be used to inform policy changes regarding treatment regimes in Scotland and elsewhere for this global pathogen.

A diagnostic real-time PCR assay for the rapid identification of the tomato-potato psyllid, Bactericera cockerelli (Šulc, 1909) and development of a psyllid barcoding database

The accurate and rapid identification of insect pests is an important step in the prevention and control of outbreaks in areas that are otherwise pest free. The potato-tomato psyllid Bactericera cockerelli (Šulc, 1909) is the main vector of ‘Candidatus Liberibacter solanacearum’ on potato and tomato crops in North America and New Zealand; and is considered a threat for introduction in Europe and other pest-free regions. This study describes the design and validation of the first species-specific TaqMan probe-based real-time PCR assay, targeting the ITS2 gene region of B. cockerelli. The assay detected B. cockerelli genomic DNA from adults, immatures, and eggs, with 100% accuracy. This assay also detected DNA from cloned plasmids containing the ITS2 region of B. cockerelli with 100% accuracy. The assay showed 0% false positives when tested on genomic and cloned DNA from 73 other psyllid species collected from across Europe, New Zealand, Mexico and the USA. This included 8 other species in the Bactericera genus and the main vectors of ‘Candidatus Liberibacter solanacearum’ worldwide. The limit of detection for this assay at optimum conditions was 0.000001ng DNA (~200 copies) of ITS2 DNA which equates to around a 1:10000 dilution of DNA from one single adult specimen. This assay is the first real-time PCR based method for accurate, robust, sensitive and specific identification of B. cockerelli from all life stages. It can be used as a surveillance and monitoring tool to further study this important crop pest and to aid the prevention of outbreaks, or to prevent their spread after establishment in new areas.

Characterisation of the British honey bee metagenome

The European honey bee (Apis mellifera) plays a major role in pollination and food production. Honey bee health is a complex product of the environment, host genetics and associated microbes (commensal, opportunistic and pathogenic). Improved understanding of these factors will help manage modern challenges to bee health. Here we used DNA sequencing to characterise the genomes and metagenomes of 19 honey bee colonies from across Britain. Low heterozygosity was observed in many Scottish colonies which had high similarity to the native dark bee. Colonies exhibited high diversity in composition and relative abundance of individual microbiome taxa. Most non-bee sequences were derived from known honey bee commensal bacteria or pathogens. However, DNA was also detected from additional fungal, protozoan and metazoan species. To classify cobionts lacking genomic information, we developed a novel network analysis approach for clustering orphan DNA contigs. Our analyses shed light on microbial communities associated with honey bees and demonstrate the power of high-throughput, directed metagenomics for identifying novel biological threats in agroecosystems.

High sample throughput genotyping for estimating C-lineage introgression in the dark honeybee: an accurate and cost-effective SNP-based tool

The natural distribution of the honeybee (Apis mellifera L.) has been changed by humans in recent decades to such an extent that the formerly widest-spread European subspecies, Apis mellifera mellifera, is threatened by extinction through introgression from highly divergent commercial strains in large tracts of its range. Conservation efforts for A. m. mellifera are underway in multiple European countries requiring reliable and cost-efficient molecular tools to identify purebred colonies. Here, we developed four ancestry-informative SNP assays for high sample throughput genotyping using the iPLEX Mass Array system. Our customized assays were tested on DNA from individual and pooled, haploid and diploid honeybee samples extracted from different tissues using a diverse range of protocols. The assays had a high genotyping success rate and yielded accurate genotypes. Performance assessed against whole-genome data showed that individual assays behaved well, although the most accurate introgression estimates were obtained for the four assays combined (117 SNPs). The best compromise between accuracy and genotyping costs was achieved when combining two assays (62 SNPs). We provide a ready-to-use cost-effective tool for accurate molecular identification and estimation of introgression levels to more effectively monitor and manage A. m. mellifera conservatories.

Microsatellite marker analysis of peach-potato aphids (Myzus persicae, Homoptera: Aphididae) from Scottish suction traps

The peach-potato aphid Myzus persicae (Sulzer) is an important vector of plant viruses. A network of suction traps collects aerial samples of this aphid in order to monitor and help predict its spatial distribution and likely impact on virus transmission in crops. A suction trap catch is thought to be a good representation of the total aphid pool. Sensitive molecular markers have been developed that determine the genetic composition of the M. persicae population. In Scotland, UK, these were applied to field collections revealing a limited number of clones. Molecular markers are less successful when applied to specimens that have been preserved in an ethanol-based trap fluid designed to preserve morphology. An assessment of different DNA extraction and PCR techniques is presented and the most efficient are used to analyse M. persicae specimens caught in the Dundee suction trap in 2001, a year when exceptionally high numbers were caught. The results reveal that the majority of the M. persicae caught belonged to two highly insecticide resistant clones. In addition, it was possible to compare the relative frequencies of genotypes caught in the trap with those collected at insecticide treated and untreated field sites in the vicinity. These results indicate that, in addition to suction trap data, the ability to sample field sites provides valuable early warning data which have implications for pest control and virus management strategies.