Asian Hornet: Why September–October 2026 Is the Most Dangerous Period

Introduction: the month when the colony reaches its peak

There is a persistent misunderstanding about the Asian hornet (Vespa velutina nigrithorax). Many people believe the danger peaks in spring, when the queens emerge from hibernation and you see those big dark insects flying past the windows. In fact, the opposite is true. In spring, a founding queen is alone, busy building a nest the size of a tennis ball, and she avoids contact. In September and October, that same colony numbers several thousand individuals, its secondary nest can exceed 80 cm across, and a proportion of the workers is assigned to defending the brood. This is precisely the moment when the future queens are born: the colony has never had so much to protect.

Unfortunately, this period coincides with the year's most "at-risk" activities: picking apples and pears, harvesting grapes, trimming hedges before winter, raking leaves, gathering the last of the vegetable garden. All of these bring a person within five metres of a nest that is often invisible from the ground, camouflaged in still-dense foliage.

There is no reason to panic — the Asian hornet is no more venomous than a common wasp, and it does not "spontaneously" attack a passer-by. But it defends its nest with far greater intensity and at a far greater distance than the wasps in our gardens. Understanding this behaviour prevents 90% of incidents.

Identifying the Asian hornet: three details are enough

The Muséum national d'Histoire naturelle (MNHN), which has coordinated reporting of the species in France since its arrival in 2004 in the Lot-et-Garonne, points out that the most common confusion is with the European hornet (Vespa crabro), a beneficial species that is protected in some regions. Three criteria let you decide in a matter of seconds, without going any closer:

Above all, remember the yellow legs. A hornet banging against a lit window in the evening is almost never an Asian hornet: it is its European cousin, which is far less problematic.

The secondary nest: autumn's real issue

In spring, the founding queen builds a small primary nest, often in a garden shed, under an awning, in a compost bin or in a roller-shutter box. As soon as the colony grows, in June and July, it moves out and builds a secondary nest high up: 10 to 15 metres up a tree, sometimes lower in a thick hedge, under roof timbers or in a bramble thicket.

This secondary nest is spherical or pear-shaped, beige-brown, with a papier-mâché appearance and a small opening on the side (not underneath, unlike wasp nests). As long as the leaves are on the trees, it is almost invisible. That is why so many nests are "discovered" in November, once the trees are bare — often when they have already been abandoned.

Golden rule: a nest discovered after the first sustained frosts is a dead nest. It will never be reoccupied the following year. Neither destruction nor call-out fees are justified.

Why hornets become more aggressive in September and October

Several factors combine in autumn, and they explain why incidents cluster in this window.

1. Production of reproductives. From late August, the colony stops producing only workers and begins rearing future queens and males. This major biological investment goes hand in hand with a reinforced defence of the nest.

2. Food shortage. Protein prey becomes scarce. Hornets fall back en masse on sugar sources: fallen fruit, split grapes, apple juice, café terraces, bins. Hence the unexpected encounters during the grape harvest or while picking apples.

3. Pressure on apiaries. UNAF and the ITSAP-Institut de l'abeille have documented for years the hornets' "hovering flight" in front of hive entrances: workers intercept foragers to feed the brood. September–October is the peak of predation, at the very moment when bee colonies must build up their winter stores.

4. Garden work. A chainsaw, a petrol hedge trimmer or even a simple telescopic pole generates vibrations that the colony interprets as an attack. The reaction zone around an Asian hornet nest is estimated at around 5 metres, compared with 2 to 3 metres for a wasp nest.

Asian hornet stings: what medicine actually says

Asian hornet venom is no more toxic than that of a wasp; the dose injected is simply slightly larger. Vidal and Ameli point out that the threat to life does not come from the toxicity of the venom but from two situations:

• An allergic reaction (anaphylactic shock), which can occur as early as the first or second sting in a sensitised person. Warning signs: swelling of the face or throat, difficulty breathing or swallowing, generalised hives, faintness, vomiting. → Call 15 or 112 immediately.
• Multiple stings (more than about ten in an adult, fewer in a child), which can trigger a systemic toxic reaction.

Also medical emergencies: any sting in the mouth, throat or near the eye, and any sting in someone already known to be allergic to hymenoptera.

What to do after a single sting

1. Move away from the area immediately: hornets release alarm pheromones that summon their nestmates.
2. Bring a heat source close (an extinguished cigarette, a hairdryer held at a distance) for a few seconds: the venom is heat-labile.
3. Disinfect, then apply cold for 15 to 20 minutes. A reusable cold gel pack kept in the freezer from August through October comes in handy far more often than you would think.
4. Remove rings and bracelets if the sting is on the hand.
5. Keep an eye on the person for at least 30 minutes.

People already diagnosed as allergic should carry their prescribed adrenaline auto-injector, and those around them should know how to use it. For families spending autumn in the garden, a first-aid kit with splinter tweezers and sterile dressings, kept within reach in the garden shed rather than at the back of a cupboard, makes all the difference in the first few minutes.

When and how to deal with a nest

Here is the question that always comes up: "I've spotted a nest in my lime tree — what should I do?"

What you must never do

• Never destroy an Asian hornet nest yourself. Off-the-shelf insecticide sprays have a range of 4 to 6 metres, well below the usual height of secondary nests, and they only kill the individuals they hit. The result: a colony on alert and an unprotected operator standing at the foot of the tree.
• Never shoot at, burn or hose down a nest: these methods cause workers to scatter en masse, and many serious accidents are recorded every autumn.
• Do not block the entrance of a primary nest in a roller-shutter box: the hornets will find another way out, sometimes into the house.
• Do not use non-selective beer or syrup traps, either in spring or in autumn. In its work on Vespa velutina, ANSES has pointed out that these homemade traps capture large numbers of non-target insects (butterflies, hoverflies, solitary bees) for very questionable effectiveness on population dynamics. If you do trap in the immediate vicinity of an apiary, choose a selective hornet trap fitted with calibrated cones and escape holes for small insects.

The sensible procedure

1. Photograph from a distance (zoom in, never approach) and report the nest on the national Asian hornet reporting platform, coordinated by the MNHN, or to your local council.
2. Contact the council: in many towns and inter-municipal authorities, part or all of the destruction cost may be covered. Schemes vary widely from one department to another — some departmental councils (notably Dordogne, Morbihan and Loire-Atlantique) have introduced subsidies, others have not.
3. Call in a specialist company, equipped with a telescopic injection pole and suits certified for "Asian hornet" work (standard beekeeping suits are not enough: the sting goes through).See our intervention services to understand how a job unfolds.
4. Cordon off the area in the meantime: hazard tape, a warning to neighbours, children and pets kept well away.

The average cost of destroying an Asian hornet nest in 2026 ranges from €90 to €250 depending on height, accessibility and urgency — a detailed breakdown of prices is given in our guide to pest control call-out prices. A nest 15 metres up that requires a cherry picker will obviously climb higher.

Protecting your garden, orchard and apiary until the frosts

In the garden and orchard

• Pick up fallen fruit every two or three days. A carpet of fermenting apples under a tree is a magnet for hornets and wasps.
• Inspect before you prune. Before using a hedge trimmer or brush cutter, watch the hedge from a distance for two minutes: a steady coming and going of insects towards a single point gives a nest away.
• Cover up. Long sleeves, trousers, closed shoes. For picking at height or working in brambles, a sting-proof protective jacket with an integrated veil eliminates the risk to the face, which is by far the most serious.
• Avoid sweet fragrances and bright colours on harvest days.
• Secure drinks outdoors: covered glasses, no cans (a hornet gets inside, you drink, and the sting happens in your mouth). Wasp-proof glass covers cost a few euros and solve the problem for every late-season gathering.

At the apiary

Amateur beekeepers, whose numbers keep growing, are on the front line. Three measures command consensus:

• Reduce hive entrances with a muzzle-type guard or an entrance reducer, which limits hornet access without hampering the foragers.
• Strengthen weak colonies and avoid any open feeding, which triggers robbing.
• Trap selectively only around the apiary, during the predation period, and never as blind mass trapping in an ordinary garden.

In and around the house

The spring primary nest is often tucked into sheltered corners: garden shed, outbuilding, roller-shutter box, disused chimney. Checking these areas in late April or early May with a good powerful torch makes it possible to spot a nest the size of an orange — a stage at which a professional can settle the problem in a few minutes, for a trivial cost. It is the best preventive investment of the whole year.

What autumn 2026 changes (and what it does not)

The Asian hornet is now present in almost every mainland French department; its spread north and east has continued in recent years, and it is listed as an invasive alien species of Union concern (EU Regulation 1143/2014). Since the law of 3 July 2024 on tackling threats to the beekeeping sector, a national control framework has been set in motion, with a designated lead officer in every department and the structuring of surveillance plans. The practical arrangements — and above all the funding of nest destruction — nevertheless remain highly variable from one area to another: always check with your local council before committing to any expense.

What does not change, however, is the biological calendar. Every colony dies with the winter; only young mated queens survive, scattered and hidden under bark or in a woodpile. Destroying a nest in December is therefore pointless. Destroying a nest in September or October, by contrast, prevents dozens or even hundreds of future queens from dispersing — that is when intervention makes the most sense, both for your immediate safety and for the pressure you will face the following year.

In summary

• The peak of danger runs from September to early November, not in spring.
• Three identification signs: black thorax, orange band, yellow legs.
• A reaction zone of about 5 metres around a nest: never go near it, never prune blind.
• No do-it-yourself destruction. Report it, contact the council, use a properly equipped professional.
• A single sting can be treated at home; multiple stings, face, throat or a history of allergy → 15 or 112.
• After the frosts, do nothing: the nest is dead and will not be reoccupied.

For more on protective equipment and selective trapping solutions suited to your situation, see our selection of pest control products. And if you have any doubt about insects flying around a hedge or roof timbers, observing from a distance is always the first step: a nest spotted early is a nest dealt with safely.