Introduction
The purpose of spring trapping is to catch and kill queens which have newly emerged from hibernation at a time when they are most vulnerable. The theory is that if they are caught and killed at this stage they can’t go on to develop their own colonies.
The foundress queen is the head of a single parent family and Mum has go out to work to provide food for herself and for her young brood. It takes about 50 days from the time the first eggs are laid to the emergence of the adult hornet (this reduces to about 29 days later in the season) and during this time the lone queen is at very high risk.
The attrition rate amongst queens emerging from hibernation is very high due to competition between them for nesting sites, a phenomenon known as usurpation, where newly emerged queens will try to kill and replace the occupant of an existing or newly constructed embryo or primary nest.
The emergence of queens from hibernation takes place over a relatively long period. Those queens waking up later do so in warmer weather, enjoy a richer food supply, and are likely to be bigger, stronger and more fertile. Trapping therefore needs to be continuous from the end of February until the end of May.
The French Connection
In France opinion is divided. In the INPN Regulations and Recommendations publication they insist that spring trapping is futile, in that for every queen you kill another, perhaps stronger queen will replace her https://frelonasiatique.mnhn.fr/lutte/#:~:text=–%20Il%20est%20possible%20de%20réduire,la%20paralysie%20de%20la%20ruche
However, in an extended study by ITSAP https://itsap.asso.fr/articles/frelon-asiatique-evaluation-de-l-efficacite-du-piegeage-de-printemps * it was shown that spring trapping can be effective but it requires:
- Trapping should only be in area where there is already an established population of Asian Hornets.
- Traps set near the site of last year’s nests that were live from September onwards when sexuals would have been produced.
- Traps to be set up in a grid-like pattern over an area of 3 sq km around the apiary.
- 59 traps to be set with a maximum distance of 350 metres between them.
- Traps set from the beginning of March (or after the last frost) until the end of May
- Traps to be emptied and refreshed at least every 8 days.
- Trapping to be repeated over at least 4 consecutive springs.
- A high level of local engagement and coordination is essential.
- Bottle-type traps to be avoided in favour of an inverted cone-shaped entry into a box of a type easily found on the Internet.
- There is a high risk of by-catch with consequences for local diversity.
This is a tall order for the beekeeper working independently and is best organised as a collective exercise within the local community.
* NB. This study has not been published in any scientific journal. There is some doubt about the results which were influenced by an unusually strong first year for AH which made the following years look better.
The Channel Islands
On the island of Guernsey a similar campaign, organized and financed by the Guernsey government, has been running for over 4 years. The whole island was covered with traps placed every 500 metres. The results for 2023 have not yet been released but the 2022 data (the 4th year of the campaign) show that out of 15 confirmed sightings, 9 queens were caught and a total of 4 nests were found and destroyed.
The Guernsey figures need to be viewed in the context of the unique situation of Guernsey as a very small island, not subject to the high rate of wind-blown inspects as Jersey, and with much less traffic in and out of its port.
By-catch
In all cases it is essential to avoid as far as possible catching insects of other species. Even if other insects are released, the effect of being captured and imprisoned with others in a highly stressful situation has an effect on them from which they are unlikely to recover, including on their survival and ability to reproduce.
Trap Design
There is at present no design of trap that can completely remove the risk of by-catch, but the least damaging is considered to be the inverted cone-in-a-box type similar to that designed by Denis Jaffré and marketed under the brand name of Jadeprod.
The Great Bait Debate
The ideal bait is one that is attractive to Asian Hornets but repulsive to all other species. As far as is known, no such bait has yet been identified. Research is underway in France at INRA in Bordeaux, CNRS in Gif-sur-Yvette, and at IRBI in Tours to identify a bait that fits this criterion.
Other experiments are under way in France and elsewhere into the use of AH pheromones as lures, but no definitive findings have yet been released.
On Jersey the commercial wasp attractant labelled Trappit (formerly Suttera) has been effective in all seasons. Several other manufacturers have entered the market with similar products that beekeepers are currently testing.
In France a mixture of equal parts of pressed fruit juice, beer and wine is recommended. It has also been found that fermented wax cappings are enjoyed by the hornets.
The seasonal variation of using protein such as prawns as bait during predation has too many disadvantages and it has been noted that forging hornets will always go for sweet flavours whatever the season.
But by far the best attractant is other hornets. Once traps have hornets in them, they will attract others very quickly.
When the trap is full the contents can be killed by immersion in water or being placed in the freezer for 24 hours.
By-catch such as the European Hornet (Vespa crabro) can be safely released after 10 minutes in the freezer (but see the remarks above about the impact on insects that have been trapped and confined.)
Conclusions
Some research in France suggests that spring trapping of queens might be effective in reducing the number of nests, but only if carried out at a high density over a prolonged period of time, in areas where there were live nests late in the previous year.
The official French Government policy remains that spring trapping is ineffective in reducing the number of nests.
Individual efforts are likely to be futile because every queen trapped is replaced by another.
The logistics involved are beyond the resources of an individual amateur beekeeper.
The danger of by-catch is unlikely to be resolved until a bait which only attracts Asian Hornets is discovered.
Alan Baxter
Area Asian Hornet Coordinator
Hampshire Beekeepers Association
23 November 2023
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