Asian Hornets: measuring and modelling the new emerging threat to managed and wild pollinators

The Asian Hornet (Vespa velutina nigrithorax) [AH] is an invasive alien species that is rapidly spreading through Europe. It is an important emerging threat to wild and managed pollinators, as it is a voracious predator of insects. Over 50% of its diet has been reported to consist of honeybees, wild bees and wasps. The AH live in large nests producing 5,000-20,000 individuals and the workers hawk for prey at bees' nest entrances, and flower patches, picking off foragers and shutting down foraging activity to the detriment of the colony. AH have caused significant damage to honeybee colonies in France and Italy with increased mortality of 5-80% where AH has established, threatening the viability of beekeeping and honey production. Of additional and immediate concern is the damage it could cause to wild bee and wasp populations, and the pollination services they provide to crops and wild flowers, but these effects have not been quantified.
An AH nest was first found in UK in September 2016, another nest found in 2017, and a third found in September 2018, signalling that establishment in the UK is imminent. The only means of halting the spread, or limiting it, is to find and destroy nests as soon as possible. There is thus an urgent need to develop a method to locate nests efficiently for management of this pest. In a ground-breaking pilot project (funded by Defra) we have radio-tracked individual AH flying back to their (previously un-discovered) nests. Our first aim is to test the range of use of radiotelemetry, and combine it with a new acoustic monitor giving early warning of AH attacks at bee hives. We will design a protocol using these technologies to reduce the speed of AH invasion (Objective 1). Our second aim is to measure the potential impact of AH as a pest of managed and wild pollinators in three ways: measuring the impact of AH predating at bee colonies (Objective 2); measure the proportions of different pollinator species in the AH diet using DNA sequencing (Objective 3) and measure whether AH disrupt pollinator networks at flower patches (Objective 4). Work will be carried out in France and the Channel Islands which are at different stages of the invasion timeline. Data on AH foraging and predation rates will be used to forecast the likely impact of these predators on managed and wild pollinators in the UK, and estimate impacts on crop pollination (Objective 5) using our models of bee colony and population dynamics, BEEHAVE and bumbleBEEHAVE.

It is essential that this research takes place as soon as possible: the best opportunity to slow a UK invasion is during the next few years. EU governments are looking for methods to slow the spread of AH, and beekeepers strongly advocate the need for investment in this work, (see Supporting Letters from Defra, DoE Jersey, and beekeepers). The ~250,000 honeybee hives in the UK are estimated to be worth £150 mill to the economy in honey and pollination provision. The AH could trigger losses of £30-45 mill per year, and our technology to detect nests early could reduce AH economic impact by at least £10-15 mill per year. This will be achieved by sharing our protocol and evidence with policy makers: to help manage the invasion and increase knowledge and skills amongst beekeepers, agencies and pest controllers. These actions, together with raised public awareness, will boost chances of early nest detection at the AH invasion front. The reduction in environmental impact will also be significant, because wild bees are under threat already, so that a further reduction in these communities is likely to affect their vitally important ecological function as pollinators.

The assembled team of researchers at Univ. of Exeter (Osborne, Tyler, Kennedy & Chaput) and partners (French researchers, Defra, Dept of Environment Jersey, the BBKA & Jersey beekeepers) have experience in animal tracking, pollinator science, molecular ecology and practical AH management to succeed in these goals.

Field work will take place in France and Channel Islands, hosted by partners with whom we have already worked. If AH is detected in the UK during the project, then field work can be adjusted to work with Defra.
Objective 1: Use new technology to find AH nests in the field: First, test our new nest-finding method of radio-tracking individual AH to explore the range of use. Then test a new acoustic early warning device, the Arnia Hornet Monitor, to signal when AH is attacking a bee hive. Outputs will be a new protocol to reduce AH spread in Europe, samples for diet identification (Obj 3), and stakeholders trained in AH identification and finding of nests.
Objective 2: Measure the impact of predating AH on honeybee and bumblebee colonies using video and remote scales at sites in France with a gradient of AH predating activity. We will record AH foraging behaviour and subsequent effects on bee colony foraging, colony growth and survival.
Objective 3: Examine AH diet to predict the effects of AH invasion on pollinator communities using next-generation sequencing to provide a complete analysis of the AH diet from returning worker food pellets, adults and brood taken from nests found in Obj 1.
Objective 4: Test whether pollinator visitation patterns to flower patches are disrupted by predating AH by observing forage patches with a gradient of AH activity, and testing its effect on the abundance, diversity and network metrics of flower visitors to those forage patches.
Objective 5: Simulate the effect of AH invasion on bee colony survival, population dynamics and crop pollination using the BEEHAVE and bumbleBEEHAVE systems models, which include a predation process in the code. Use data from Obj 1-4 on AH foraging choices and impact to run scenarios of the likely effects of the AH pest on honeybee colony survival and bumblebee populations over years. Results will also show impact on crop visitation in modelled landscapes, giving an indication of pollination effects.

The project will be deemed successful if the following practical outcomes are achieved:

- Our nest detection protocol is used on the front line of AH invasion in Europe by practitioners and professionals.
- EU governments tackling the spread of this pest use our evidence and predictions to shape policy on AH management, and it is added to the National Pollinator Strategy in the UK.
- Beekeepers, bee farmers and the general public have an increased awareness of AH.

The above outcomes lead to an overarching ENVIRONMENTAL IMPACT of slowing the spread of AH in the UK, and lower subsequent mortality of honeybee hives and wild pollinators. This will also have an ECONOMIC IMPACT because it will lead to cost savings compared to the unchecked spread of the hornet, in terms of honeybee colony management costs, beekeeping profits, farmers depending on insect pollinators, and also the overall long term costs of managing an invasive species. Because of the technology we are promoting it would also result in profit enhancement for the small UK companies (Biotrack and Arnia) selling radio-telemetry and early warning monitors for use in AH management.

WHO WILL BENEFIT and HOW?

Beekeepers and Bee farmers: This group stand to benefit most immediately from the finding and destruction of AH nests in the vicinity of their apiaries. AH could have a larger impact on reducing colony numbers and honey yields than the impact of the Varroa mite in the 1990s. Using similar methods to those used to estimate Varroa impact, our calculations suggest that if our protocol and evidence results in reducing AH nest density even by 30%, then this could save £10-15 million per year in lost profits. We already work with a large group of volunteer beekeepers (South West UK beekeepers, the BBKA, and the beekeepers on Jersey) who will be involved, and we will run training workshops to demonstrate how to detect and find AH nests so that we build a trained and engaged community, who will be at the front-line of AH detection.

National Bee Inspectors, Defra and Policy Makers: who are developing regulatory policy on bee health, pest and disease management. They need a route map to make decisions about how to manage the AH invasion, and the costs associated - our empirical evidence and new tools will support this crucial work. They are also implementing the National Pollinator Strategy which should include responses to AH distributional changes. As has been seen in France, the long term management costs of an invasive species can quickly exceed eradication costs in the early stages of invasion. So methods that can promote early eradication, or even confinement into small areas, will result in significant economic (and ecological) pay off.

Society: There is wide and impressive support from the public for bee-friendly initiatives and policies, and individuals are taking responsibility to improve pollinator populations. The results of our project will lead to greater awareness of AH and possibly earlier detection. It will inform discussion around invasive species, and we will run a Creative Exchange Project, working with a film-maker to create a short video for a public road show across Southern England (where AH incursions have already been made) on 'Bees vs Hornets; Who Decides?', to provoke thinking about the complexity, costs and benefits of managing invasive alien pests effectively.

Whilst it is not yet feasible to accurately measure AH population density, and the longer term ENVIRONMENTAL and ECONOMIC impacts of curtailing the establishment of AH in the UK are not measurable within the lifetime of the project, our tracking technology and evidence base will provide a toolkit to support the protection of wild and managed bees, and consequently pollination, by enabling good decision-making in relation to management of this invasive pest species.