Lessons Learned: AGH Prevention and Preparation

Editor’s note: Conrad Berube, an entomologist and beekeeper (and senior IPM officer with the British Columbia Ministry of Environment), has spent more than 40 years working with highly defensive stinging wasps and bees, particularly tropic-zone evolved honeybees (so called “killer bees”), in North, Central and South America, Asia and Africa. Berube has been the triggerman for the 2019 extirpation of the first (and so far only) nest of Asian giant hornets (Vespa mandarinia) discovered in Canada¹. Berube has written a full-length feature geared towards pest management professionals that includes a description of the basic biology of social wasps; information on the identification of Asian giant hornets (AGHs) and their kin; personal protection recommendations; and tips for safe nest removal. (Read the entire article at bit.ly/3oaDdmD.) The following is an excerpt from that article that deals with AGH prevention and preparation.

In August 2019, Nanaimo, B.C., beekeeper John Duff collected unfamiliar, very large wasps harassing bees at his backyard beehive. He sent specimens to B.C. Provincial Apiculturist Paul van Westendorp, who confirmed these as the first specimens of the Asian giant hornet (AGH), Vespa mandarinia, found in North America. Notified of the find, John and Moufida Holubeshen, Nanaimo Beekeepers Club officers, near miraculously, discovered their nest during a dusk visit in a nearby park — immediately after which they called me to take it out.

Since that first encounter, I’ve been called upon in a variety of capacities related to AGH, including as a presenter to members of the Canada Pest Management Association. I encourage any pest management professional interested in becoming involved in AGH monitoring/control efforts to read the entire article (referenced in the editor’s note) as a first step.

This article will focus on the prevention and preparation steps of IPM as they relate to Asian giant hornets.

GOVERNMENT ACTION. As they are native to Asia, routine border protections are the first line of defense in preventing introductions of AGH — and any other potential pest species. The Canadian Food Inspection Agency has treatment and inspection programs that reduce the chance of pests crossing borders as stowaways in freight. Live AGH larvae have been seized at border crossings, presumably from folks wishing to use them in food or drink preparations. Such precautions are not always effective, and researchers in France traced the introduction there of another Asian hornet, Vespa velutina, the yellow-legged hornet, to a shipment of flowerpots from China². Stacks of earthenware pots contain gaps that hornet queens could enter through the drainage holes — resembling, as they do, preferred overwintering sites. Springtime loads of terra-cotta flowerpots, bound from Asia for the nursery industry, could contain stowaway AGH queens. Apparently, something similar occurred to allow AGH queens to establish nests near the British Columbia/Washington border in the past several years.

On Sept. 19, 2019, following up on nearby specimen catches by a fellow Nanaimo bee club member the month before, the Holubeshens made the sunset discovery of the first Asian giant hornet nest in North America. Along with bee club president Lange and myself, we traveled to the site and began preparing ourselves for the coming confrontation. Reducing stings was at the forefront of our minds since we had read about the necrotic tissue damage that can result from the stings of AGH. The venom of Asian giant hornets is likely no more potent than that of other stinging Hymenoptera, but, because of their large size, they can deliver a greater dose in any single sting — the venom load of an AGH worker is about 0.0041 cubic centimeters (that volume being equal to roughly half that of an average human tear).

The key to reducing sting incidents is by managing the components of what I have come to think of as the sting triangle (analogous to the fire triangle for combustion). If you can reduce or eliminate any component of the triangle, you can lessen the risk of stings. If you eliminate the bee or wasp population, there is no risk of stings. If you can prevent disturbance to the wasps or bees, there is no risk of stings. If you can prevent yourself from being a target, there is no risk of stings.

Captured hornet: Hector Castro | WSDA

Our goal was to eliminate the hornets — by which we were, out of necessity, going to cause a catastrophic disturbance to the colony. So the component for which we could exert the greatest amount of control was in protecting ourselves as targets. In this, we used many techniques that echo those that honeybees employ.

Much like the eastern honeybees that make speedy return flights when encountering AGH, the simplest tactic to avoid stings is to beat a hasty retreat. Should you be caught without gear and disturb a wasp nest, shield your eyes with your fingers to protect your vision and beat it out of there as quickly as possible. On flat level ground, most of any pursuing workers will give up the chase within a few tens of meters (about the length of a basketball court)³. If present, dodge through leafy vegetation to conceal your retreat and brush away any persistent pursuers.

With the luxury of prep time, we can employ other techniques that are utilized by honeybees — such as the element of disguise. For example, eastern honeybees smear foraged feces at their hive entrances that masks hornet pheromones. This is an important tactic that should be imitated when working around stinging Hymenoptera — but it need not involve dousing oneself with feces. (Although, by an odd coincidence, while preparing this article I heard a podcast in which it was mentioned that during World War II the Irish parliament building was daubed with dung and coal dust to camouflage its distinctive stonework from air raids — and it has never been successfully restored to its original color⁴.)

Beekeepers routinely use smoke to mask the smell of alarm pheromone at a sting site, so you don’t need to bother with a bee-bellows; slathering on some liquid smoke over the face and head can similarly reduce the chance of being stung — if a wasp is able to work its way under one’s veil. Wasps and bees taste with their feet, and essentially the smoke flavoring will act as a repellent when the stinging insect is attempting to position itself on your skin to sting, giving you enough time to step away from the nest, mash the insect inside your veil and to remove it before returning to the nest area. (As an aside, beekeepers also puff a little smoke into hives before working with them because it causes the workers to busy themselves with eating honey, which will fuel their escape if the nest needs to be abandoned. Bloated with honey, the bees are more reluctant to rise from their combs and are slower to sting.) The honeybee sting mechanism is barbed, and a bee disembowels itself and dies soon after leaving its syringe-like venom sac behind. If stung by a bee, you can at least take some solace that the bee got the worst of the bargain. Nonetheless, the disembodied venom sac will continue to pump toxins into the skin — if not immediately flicked off with a thumbnail or like remover.

HAVE FIRST AID HANDY. In contrast, wasp sting lancets are smooth, and a single worker can sting repeatedly. The sting organs of Hymenoptera are modified from the organs that, in other insect species, such as parasitic wasps, form ovipositors. So the male bees and wasps, the drones, cannot sting. Most of the individuals in a colony are, however, fully-armed female workers, so it’s good practice to have a supply of first-aid equipment handy when tackling nest removal. Those who are severely allergic to wasp or bee stings often carry an EpiPen to prevent anaphylactic shock — but these devices would be overkill for the normal pain and swelling that one would expect from being stung. I received at least seven stings in the course of removing the nest. The first four were the worst of those stings, and felt like red hot thumbtacks being driven into the flesh. Two of the first/worst stings drew blood and the resulting scars were still evident a year later.

Within a few hours of receipt, I took a couple of ibuprofen for the persistent pain from the four stings I’d sustained across the thighs — but I didn’t bother with an antihistamine to reduce swelling (to which I am not much prone given my long history of exposure). However, pest control professionals may want to include a supply of these if they are going to be taking out any kind of wasp nest. I didn’t swell very much, but for the next 24 hours or so, I had throbbing in my legs similar to the muscular ache one often gets with flu.

Getting back to our preparations for the nest assault, in addition to a hickory-flavored face wash, we bolstered our normal beekeeping gear, veiled bee suits and long-sleeved, heavy gloves with extra-thick clothing. As I had volunteered to conduct the actual nest extraction with the Holubeshens and Lange acting as support crew (and potential medevac team), I was also sporting Kevlar bracers at wrists and ankles and a bulletproof vest of the kind normally used for chainsaw safety or in zombie apocalypses. In hindsight, that was a bit of overdressing.

NIGHTTIME IS THE RIGHT TIME. Night had already fallen, making it the ideal time for dispatching a wasp nest. Social Hymenoptera largely return to their nests at day’s end — although occasional stragglers may get caught by the dark, in which they cannot fly, and then overnight outdoors — so the great majority of the colony is in the nest at nightfall. It is in such conditions that wasps who build aerial nests can be collected with their entire population by simple bagging — with minimal risk to the collector or bystanders. The collection of enclosed or subterranean nests is a bit more complicated but, likewise, is ideally performed at night. Even at night, appropriate personal protective equipment (PPE) should be used along with other gear necessary for nest removal.

Alpsdake | Creative Commons

Now, keep in mind that I said wasps and bees don’t fly in the dark; if you are using lights to see what you are doing while you collect such insects, it’s no longer dark. Wasps and bees will fly toward headlamps worn by nest raiders, so, it’s recommended that you set up a light source detached from your person to illuminate your work, using your headlamp intermittently as necessary. Once properly girded, comparisons are naturally drawn between wasp hunters and ghostbusters, either because of similar Canadian fashion choices or because the high-end protective garb favored by WSDA collectors makes them resemble the Stay Puft Marshmallow Man.

PROPER PPE. There’s a huge difference in price ranges on anti-sting wear. I wear a low-cost bug jacket that is cool in the hot weather, in which I often work, and which can easily be bolstered with extra layers of clothing. Frankly, I think the high-end suits favored by the WSDA, if used by less diligent personnel, might promote a cavalier attitude that could result in cutting corners on safety protocols, such as removing nests near dwellings during daylight hours — which could expose unprotected bystanders to sting risks if used for routine wasp removals — or if AGH eradication becomes a more commonplace necessity.

Whatever your outerwear choices are, it’s a good idea to wash or rinse down protective gear if any significant amount of alarm pheromone has been deposited on it during sting incidents. In addition to PPE, the following are recommended: flashlights and headlamps; collection bottles and containers; garbage bags; isopropyl alcohol; a carbon dioxide fire extinguisher; a vacuum cleaner; aerosol wasp and hornet killer; a shovel; a small saw and large knives; and a tote to carry everything in the kit.

References

¹ Milius, S. 2020. What you need to know about ‘murder hornets’. Science News for Students. https://www.sciencenewsforstudents.org/article/what-you-need-to-know-about-murder-hornets

² Arca, M., Mougel, F., Guillemaud, T., Dupas, S., Rome, Q., Perrard, A., ... and Silvain, J. F. (2015). Reconstructing the invasion and the demographic history of the yellow-legged hornet, Vespa velutina, in Europe. Biological Invasions, 17(8), 2357-2371. https://www.researchgate.net/publication/ 276026354_Reconstructing_the_invasion_and_the_demographic_history_of_the_yellow-legged_hornet_Vespa_velutina_in_Europe

³ Kim, D., Jung, C., Lee, S., Kim, Y., Noh, G. R., Lee, H. S., ... and Bang, K. W. (2019). 181 Study on Defensive Behavioral Mechanism of Vespa Hornets by Anthropogenic External Disturbance. https://www.researchgate.net/publication /337035088_Study_on_Defensive_Behavioral_Mechanism_of_Vespa_Hornets_by_Anthropogenic_External_Disturbance

⁴ Northern Ireland Assembly. Parliament Building Facts. http://www.niassembly.gov.uk/assembly-business/office-of-the-speaker/80th-anniversary-open-day/parliament-buildings-facts/

⁵ de Brito Sanchez, M. G., Lorenzo, E., Songkung, S., Liu, F., and Giurfa, M. (2014). The tarsal taste of honey bees: behavioral and electrophysiological analyses. Frontiers in behavioral neuroscience, 8, 25. https://www.researchgate.net/publication/ 260254469_The_tarsal_taste_of_honey_bees_Behavioral_and_electrophysiological_analyses