Monitoring for Northern Giant Hornets Continues

Editor’s Note: Now is a critical time to monitor for the invasive Asian giant hornet (AGH), which recently was renamed the northern giant hornet (NGH) by the Entomological Society of America. In late summer, colonies of Vespa mandarinia begin to produce males and next year’s queens, and workers leave nests in search of high-protein food to feed these new young. In fall, males and new queens leave the nest to mate. The mated queens then look for a place to overwinter. They start new colonies in spring. The first NGH nest in North America was discovered in September 2019 in Nanaimo, B.C. Since then, four NGH nests have been removed in neighboring Washington state.

Conrad Berube, entomologist, beekeeper and senior integrated pest management officer with the BC Ministry of Environment & Climate Change Strategy's Compliance and Enforcement Unit, has spent 40 years working with stinging insects. He was the triggerman for the 2019 extirpation of the NGH nest discovered in Canada. Berube has written a full-length feature for pest management professionals that explores the basic biology of social wasps; information on the identification of NGH and their kin; personal protection recommendations; and tips for safe nest removal. Read the entire article from PCT here. The following is an excerpt from that article that describes monitoring efforts for the invasive pest.

As is usually the case in the structural industry, it is very likely that initial monitoring to detect the presence of pest wasps, including the AGH, is going to be conducted by your clients. For run-of-the-mill wasps, clients will likely contact you only after they have visually located a nest on their property. But you may occasionally be contacted by someone who believes they have trapped an AGH and wants you to do something. 

There is no legal requirement to report AGH, but you are certainly encouraged to do so. At least, that's the case for most people. Beekeepers in B.C. are required to report novel diseases impacting their bees (which, oddly, includes insects under the legal definitions) under the provincial Bee Act. In B.C., reports can be made with a photo attachment of the suspected AGH, via email, to info@bcinvasives.ca, but you can also use the Washington State Department of Agriculture (WSDA) reporting venues, including hornets@agr.wa.gov or aghtrapping@agr.wa.gov.  

The Canadian Food Inspection Agency monitors for a variety of potential pest species. After the Vespa soror specimen turned up near Vancouver’s port, the Canadian Food Inspection Agency deployed some commercial wasp traps to monitor for additional hornets. It was only after our Nanaimo extirpation that I advised their reps that those traps had apertures too small to allow entry of the wasps for which they were intended. The commercial traps had to be altered by boring larger entries to serve in monitoring for Asian hornets — but much more economical alternatives can be made by recycling 2-litre soft drink bottles. 

The design is simple enough that you’d likely be able to come up with a workable unit just from seeing an example, but detailed instructions can be found on a WSDA site — and, as mentioned, citizens living near the B.C./Washington border are encouraged to participate in trapping programs and to report catches or incidental sightings of AGH. A graphical database of such reports, including confirmed identifications of AGH, is maintained by the WSDA.

Many beekeepers are participating in AGH monitoring programs. Some already routinely use devices intended to prevent wasps from preying on hives, as established yellowjacket species cause significant bee losses. Sticky traps are the preferred method of dealing with AGH harrying western honeybee colonies in the native range of the hornets and likewise, in temperate zones, are more effective than bottle traps — if the AGH nest cannot be located. For yellowjackets, a water bath trap baited with meat or fish will not attract bees and seems to be more effective than bottle traps. 

But any such trapping is only good enough to indicate that a nest may be active in the area. More laborious methods are required for locating nests, and, frankly, those are probably best left to parties working with the government to prevent the establishment of AGH, as the exercises are likely to be time-consuming or otherwise prohibitively expensive.  

The WSDA has used radio tags small enough to tie to live-trapped hornets to track them back to their nests and has been experimenting with infrared spotting technology. As a traditional alternative, streamers can be attached to balls of fish left out as bait for hornets to carry back home or to the hornets themselves to assist in visually following released hornets to their nest.

Key points on monitoring:

• Most trapping is conducted by citizen scientists, especially beekeepers, and any suspected AGH caught in traps, or incidentally spotted, should be reported.
• WSDA has used radio-tagged hornets to locate four nests so far.
• It’s likely not worth attending to a complaint of AGH, or other wasps, unless a prospective client reports a nest location