Should Asian hornet traps be installed towards the end of the summer?

Reader question: I’ve started seeing more Asian hornets in my garden in August. Should I put out traps now, or will they do more harm than good? 

Even though Asian hornet activity increases towards the end of summer, it is not recommended to install traps in gardens or around homes.

The Office for Insect and Environmental Studies (Office pour les insectes et leur environnement, OPIE) said that attacks on honey bees “increase as the season progresses and reach their peak in September and October”. 

This is the period when large colonies can put significant pressure on beehives, particularly in areas with many apiaries.

However, the OPIE warned that widespread trapping can harm biodiversity because “non-selective traps kill millions of insects”. 

These include wild bees, honey bees, butterflies, hoverflies, native wasps and other pollinating insects. Some of these insects are important pollinators, while others help regulate populations of other insects.

For this reason, the OPIE said trapping should be limited to specific situations: “The use of traps should be restricted to the area around apiaries affected by the presence of yellow-legged hornets.” 

Targeted traps may therefore be used by beekeepers when their hives are under heavy attack, but they are not recommended as a general solution.

The late summer period is, however, important because colonies begin producing future queens. DRAAF Auvergne-Rhône-Alpes (a regional French government service) states that “from mid-August to the end of September, the colony is raising the reproductive individuals”. 

The first new queens emerge at the end of September, which is why “it is important to destroy as many nests as possible before this date”.

Destroying nests before new queens leave is intended to reduce the number of new colonies that can establish themselves the following year.

Jérémy Riand, a hornet-control professional at Stop Frelons 85, advised against relying on traps at this time of year. He said trapping is more useful earlier in the season, when queens are emerging and establishing colonies.

“You have to do it in February, March and April to be able to trap the queens. If you trap a queen, that means one less nest,” he told The Connexion. 

By late summer, he said, the queens remain inside the nest while workers are outside.

“At this time of year, you are going to trap workers because the queens are no longer coming out of the nest.”

As a result, catching a small number of workers is unlikely to make much difference to an established colony.

“You might trap three workers, but in the nest, which shouldn't be far away, 15 more may be born. It is no longer really useful to trap them. It may limit the numbers, but it isn't going to achieve much.”

What to do if you find a nest

If you find a nest at your home, garden or shed it is important to not attempt to remove it yourself. Keep a safe distance, even if it appears small and harmless, and make sure children and pets stay well away.

August is a particularly sensitive period because secondary nests reach their peak activity. Colonies can contain thousands of individuals by this stage, and the hornets become more defensive as they protect the colony and the queen. 

Vibrations or loud noises from activities such as mowing, hedge trimming or disturbing branches near a nest can trigger a collective defensive response.

Mr Riand warned that disturbing a large nest can result in a very large number of hornets responding at once.

“When the nest is large enough, if you try to destroy it, you can have 200, 300 or 400 hornets coming at your face, your legs and your arms.”

He therefore advises homeowners to call a professional rather than attempting to deal with the nest themselves.

If possible, take a photograph of the nest while keeping your distance, using zoom and no flash, so that its location can be accurately recorded. Then report it to your local mairie or to certified professionals.

Depending on your area, local authorities will either direct you to a specialist or arrange for the nest to be removed.