Why Asian hornets are a bigger concern at the end of summer in France

If you have started seeing more Asian hornets in your garden in August, there is a good reason for this: the period from mid-August to the end of September is very important in the hornet's life cycle.

DRAAF Auvergne-Rhône-Alpes (a regional French government service) said this is when “colonies are raising their reproductive individuals”. The first new queens emerge towards the end of September, which is why nests should be destroyed before then. 

Asian hornets are an invasive species in France, and can now be found almost everywhere in the county. 

Are Asian hornets more aggressive in August?

The Office for Insect and Environmental Studies (Office pour les insectes et leur environnement, OPIE) said Asian hornets are not generally more aggressive towards people than other types of wasps and hornets.

The real issue is the size of the colony. By late summer, a nest can contain a large number of hornets (up to 300-400) as secondary nests reach their peak activity. It is a very important time for Asian hornets as it's the time the first new queens emerge. 

If the nest is disturbed, the colony can become defensive, creating more risk that you will be stung by multiple hornets.

“Whether it is the middle or the end of the summer, their behaviour remains the same. It is simply that there are more of them in the nests. So the attack will be more significant at the end of summer than at the beginning or middle,” Jérémy Riand, a hornet-control professional for Stop Frelons 85, told The Connexion.

He said a large nest can contain hundreds of hornets capable of responding when it is disturbed. 

“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 said. 

This means activities such as mowing the lawn, cutting a hedge or pruning a tree can become dangerous if a nest is nearby and has not been identified.

What should you avoid?

If you suspect there is a nest nearby, avoid disturbing the area. If you identify one you should under no circumstances try to hit it, shake it, throw objects at it, spray it with water or household insecticide or knock it down. 

You should also avoid using machinery such as a hedge trimmer or lawnmower in the immediate vicinity of the nest because the noise and vibration can threaten the hornets resulting in attacks.

“If you are not properly equipped, it is very, very dangerous. It often ends very, very badly,” Mr Riand said.

In the worst cases, he said, people can die after multiple stings; in less serious cases, victims can require emergency treatment and hospitalisation. 

A warning against DIY nest removal

Mr Riand gave an example of a woman who contacted him after finding a hornet nest at her home.

After being told the price of professional treatment, she decided that her husband would deal with it himself.

“She told me, ‘For that price, my husband will do it.’ I warned her: ‘Be careful, it is dangerous. These aren't mosquitoes, they aren't flies - they are hornets.’”

The man attempted to protect himself with a motorcycle helmet, a scarf, gloves and a leather jacket.

Around 20 to 30 minutes later, his wife called the professional again.

“She called me saying that he had been stung and that they were going to the emergency department. She said she would call me back that afternoon so I could come and treat the nest.”

The example showcases that homemade protective equipment should not be regarded as sufficient protection against a large, established nest.

How can you identify a nest?

One of the biggest risks is accidentally disturbing a nest that has not been seen.

Mr Riand said particular care should be taken when cutting hedges. “When you have to cut hedges, you should give the hedge a big sweep with a rake while keeping your distance, to see whether anything comes out.”

If hornets emerge from a particular area, he said this could indicate a nest. “If there is a nest, obviously you don't cut the hedge. You call a professional and then you cut the hedge afterwards.”

Another warning sign is repeated insect activity at a single point. “You see insects coming out and going back in at a fixed point. That is when you realise there is a nest, whether it is under roof tiles, underground or in a particular location.”

If you see hornets repeatedly entering and leaving from the same spot, avoid approaching or disturbing the area and arrange for the nest to be assessed.

What if you find a nest?

If you find a nest you should keep your distance and make sure children and pets stay away and not try to remove it yourself. 

ANSES (the French health agency) recommends keeping at least five metres away from a nest and informing other people who may be at risk of approaching it. 

He said there is a limited exception very early in the season where it is possible to carefully destroy it yourself, when a nest is still very small and contains only the queen.

“At the very beginning of the season, when the nests are the size of an orange, when they are small and there is only one queen inside, it is possible, strictly speaking, to treat them at night with a specific hornet insecticide. It is not recommended, but it is possible,” Mr Riand said.

However, once worker hornets are present, he said homeowners should not attempt treatment themselves.

“As soon as there are workers, you can no longer control the situation. You can have three, four or five workers coming at you, even at the beginning of the season, and you cannot manage it. You simply have to call a professional.”

Should you put out a trap?

An important thing to note is that seeing Asian hornets in your garden does not necessarily mean you should put out a trap.

This is because non-selective traps can also kill many other insects, including bees and other pollinators.

At the end of the summer, the use of trapping is restricted only for around beehives that are being attacked by Asian hornets (thus to beekeepers), rather than using traps generally in gardens.

How much does it cost to remove an Asian hornet nest? 

The cost of professional treatment varies depending on the size and location of the nest.

Mr Riand estimated that an intervention would typically cost between €90 and €200, although the price depends on factors including the height of the nest.

A nest at ground level will generally be easier to reach than one located high in a tree, for example.

Some French local authorities and collectivités also contribute towards the cost of nest removal. “Fortunately, some town halls cover the cost of the removal or part of the cost,” he said.

This means that you can report the nest to your local mairie or to a certified professional. Depending on where you live, the mairie can tell you who is responsible for arranging its removal.