Asian Hornets in September 2026: The Month of Peak Aggression and Nests Found Too Late

There's one call we receive every year from 1 September onwards, and it almost always begins with the same sentence: "I've just found a huge nest in the lime tree at the bottom of the garden. It wasn't there before."

It was there. Since May, sometimes April. It was simply the size of a golf ball, hidden in the foliage, and no one had any reason to look up. By September, it measures 60 to 90 cm across, houses several thousand workers, and a single pass with a hedge trimmer five metres away is enough to trigger a mass attack.

The Asian hornet — Vespa velutina nigrithorax — has been present in France since 2004 and has colonised virtually the whole country, Île-de-France included. It is classified as an invasive alien species and appears on the list of category two health hazards for the honey bee (decree of 26 December 2012). But what concerns us here is the calendar: September and October account for the overwhelming majority of nest destruction call-outs, and this is also the period when serious accidents occur.

Brown rat walking through grass at the water's edge, snout turned towards the lens

Why September is the most dangerous month

The colony cycle, in plain terms

An Asian hornet colony is annual. It is born, grows, reproduces and dies within a single season. Understanding this cycle means understanding why your neighbour noticed nothing for four months.

Three practical conclusions follow from this table.

One. The nest you discover in September is at the height of its strength: according to the Muséum national d'Histoire naturelle and INRAE, a mature colony can produce several thousand individuals over the season, with a peak of around 1,000 to 2,000 workers present at any one time.

Two. At this stage, the colony is protecting its future founding queens — the only asset that will survive the winter. The defence perimeter widens considerably: it is generally accepted that approaching within 5 metres, and above all any vibration transmitted to the support (pruning, ride-on mower, pressure washer, ladder leaned against the tree), can trigger a mass sortie.

Three. Destroying a nest in October, once the founding queens have already left, is of no further use in controlling the species — but it still makes complete sense for your safety if the nest is close to a thoroughfare.

The "falling leaves" factor

The second wave of calls arrives in late October, when the trees shed their leaves. Many nests are never spotted all season and only appear at that point, sometimes empty. Hence a piece of advice we repeat constantly: before jumping to conclusions, watch the traffic. An active nest shows a continuous stream of insects entering and leaving through a side opening, visible with binoculars from a window. A pair of compact binoculars is genuinely useful here, and saves you from moving closer to "get a better look" — precisely the move that sends people to A&E.

Identifying it: Asian hornet, European hornet, wasp

Confusion is costly in both directions: people have European hornet nests destroyed (a native, useful and fairly good-natured species) while leaving velutina nests alone.

The most reliable marker, from a sensible distance: yellow legs + black thorax = Asian. And a hornet banging against your patio door at 11 pm is a European hornet, never an Asian one.

One point that rarely reassures anyone but is well established: Asian hornet venom is no more toxic than that of the European hornet or the common wasp, as ANSES points out. The danger comes down to three other factors: the quantity injected per sting, the number of stings in the event of a colony attack, and individual allergic risk.

Two rats, one brown and white, the other white, sitting on a stone in front of green foliage

Stings: what to do within ten minutes

The recommendations below draw on the guidance sheets from Ameli and Vidal. They obviously do not replace medical advice.

A single sting, with no history of allergy

1. Move away first, calmly but without dawdling, 20 to 50 metres, avoiding running while waving your arms. Never take refuge underwater: hornets wait at the surface.
2. Clean with soap and water.
3. Bring a heat source close (the tip of an extinguished cigarette a few millimetres away, hot water) for a few seconds: the venom is heat-labile.
4. Then apply cold — a reusable gel pack wrapped in a cloth — to limit swelling and pain.
5. Monitor for 2 hours. Intense but localised pain, redness, moderate swelling: that's the normal reaction.

A venom extractor pump works no miracles on a hymenopteran sting but remains a useful item in a hiking first aid kit, alongside the cold compress and any antihistamines your doctor may have prescribed.

Situations that require calling 15 (or 112)

Call the emergency services immediately if: multiple stings (from around ten in an adult, fewer in a child); a sting in the mouth, throat or near the eye; swelling of the face or lips; difficulty breathing, wheezing, hoarse voice; generalised hives; faintness, dizziness, drop in blood pressure, vomiting.

These signs point to an anaphylactic reaction, which can develop within minutes, including in someone who has been stung before without any problem. Anyone who has had a generalised reaction should have a prescribed adrenaline auto-injector and know how to use it; desensitisation (allergen immunotherapy) is possible and effective, and should be discussed with an allergist.

What you must never do

The list is short and non-negotiable. Every year, fire and rescue services report serious accidents linked to DIY destruction attempts.

• Never douse a nest with petrol, white spirit or paraffin. Risk of fire, explosion, soil contamination — and an immediate attack.
• Never shoot at it with a shotgun or airgun. The nest opens up, the entire colony pours out, and the shooter is out in the open.
• Never empty an over-the-counter insecticide spray onto a nest high up: the range is insufficient, the product doesn't penetrate to the heart of the nest, and you place yourself under a rain of workers.
• Never take down a nest, even one presumed empty, without having watched it for several consecutive days in sunny weather.
• Never block the entrance of a nest in a cavity (roller shutter box, chimney): the hornets will come back out into the inside of the house.
• Don't climb a ladder. Almost all serious injuries come not from stings but from the fall caused by panic.

Having a nest destroyed: how it actually works

Who to call

Contrary to a persistent belief, the fire brigade no longer routinely attends wasp and hornet nests on private property: since the reform of "call-outs falling outside public service missions", they reserve themselves for situations of imminent danger (a nest in a school, a nursery, a public building, or a person trapped). For a garden or a façade, destruction is the job of a specialist pest control firm (rodent control, insect control, disinfection), holding the Certibiocide certification and equipped accordingly.

Some Île-de-France councils and inter-municipal authorities contribute financially to the destruction of Asian hornet nests: it is always worth calling the town hall before booking the job, and asking for an itemised invoice stating the species.

How a call-out unfolds

A properly conducted destruction comes down to four stages:

1. Survey and assessment: species confirmed, height, support, distance to openings, presence of beehives, a water point, children or animals.
2. Securing the perimeter: windows closed, neighbours warned, area cleared for 10 to 20 metres.
3. Injection: the technician, in a full reinforced anti-hornet suit (a simple beekeeper's outfit is not enough, the sting reaches up to 6 mm), injects insecticide powder directly into the nest via a telescopic pole. The colony is neutralised within a few minutes to a few hours.
4. Removal of the nest where accessible — recommended, to prevent other insects from feeding on the residues, and to remove any doubt the following season.

The work is preferably done early in the morning or at the end of the day, when all the workers are back inside. Never in the heat of the afternoon, when a third of the colony is out flying.

Prices observed in Île-de-France usually range between €90 and €250 depending on height and accessibility, with surcharges for nests requiring a cherry picker. Be wary of adverts at €49: they regularly end with a quote multiplied several times over on site.

Brown rat at the edge of stagnant water, on damp stones covered in moss

Prevention rather than damage control: the useful calendar

Spring trapping, yes — but done properly

Trapping founding queens is done from late February to mid-May, never in autumn. Mass, non-selective trapping in summer or September mainly catches butterflies, solitary bees, hoverflies and European hornets: the ANSES report on the subject is unambiguous about the collateral damage.

If you do trap, use a selective hornet trap with calibrated openings (roughly 5.5 mm to 8 mm) allowing smaller insects to escape, with a sweet, alcoholic bait such as dark beer + blackcurrant syrup + white wine (the alcohol repels bees). Check it regularly. Position it near flower beds and compost bins, not against the house.

The April inspection, the real game changer

The single most worthwhile action of the whole year takes ten minutes on a Saturday in April: walk round the garden shed, the garage, under the eaves, the rarely used shutters, the dense hedges, looking for a primary nest the size of an orange. At that stage there is only one founding queen and a few larvae: a targeted destruction in the evening, from a distance, with a long-range wasp and hornet insecticide spray, solves the problem and saves you an entire season. After June, forget it: call a professional.

Reducing September's appeal

Late in the season, workers are looking for sugars. That's when they become intrusive around terraces and orchards.

• Pick up fallen fruit (apples, plums, figs) every couple of days.
• Cover bins and compost heaps; rinse cans and bottles before recycling.
• Protect outdoor meals with insect-proof food covers, more effective and far less aggressive than a spray.
• Avoid heady floral perfumes and flower-print clothing when eating in the garden.
• Don't leave bowls of wet cat food outside: it's a protein source that attracts foraging workers.
• Fit magnetic insect screens for patio doors if you live near an orchard or an apiary.

What about bees?

If you are a beekeeper or live next to an apiary, September is also the month when hornets hover in front of hive entrance boards, picking off foragers on their return. The pressure can block departures and seriously weaken the colony before overwintering. Entrance muzzles and electric harps do produce results, but the most effective measure remains destroying the nest or nests within a radius of a few hundred metres.

Key takeaways

The Asian hornet is not a killer, and the collective panic surrounding it does more damage than the insect itself: the vast majority of stings occur because someone got close to the nest, not because the insect went out hunting humans. Away from a nest, the Asian hornet is in fact remarkably unaggressive — it flees.

The right reflex in September comes down to three lines:

Spot it from a distance. Don't tackle it yourself. Bring in a properly equipped professional, early in the morning or in the evening.

And pencil into next spring's diary a ten-minute inspection around the house: that's where the season is won, not in October at the foot of an 80 cm ball.

If you have any doubt about the species, about whether a nest is active, or about what to do, our teams are available 7 days a week across Île-de-France for assessment and safe destruction.