Asian Hornets and the 2026 Grape Harvest: Why September Is the Most Dangerous Month

Introduction: the month the colony peaks

There is a stubborn gap between public perception and the biology of the Asian hornet. Many people assume the danger lies in spring, when queens emerge from hibernation and build the first primary nests. That is wrong — or at least very incomplete. In France, the peak risk period is September and October.

At that time of year, a colony of Vespa velutina nigrithorax established since spring can number several thousand individuals, its secondary nest can reach the size of a rugby ball or even a 100-litre bin, and above all: its food requirements explode. The colony is producing its future queens and males, which demands a massive intake of sugars. The hornets then turn to whatever is available — ripe grapes, apples, pears, figs, insect carcasses, apiaries, restaurant terraces.

This is exactly the moment when the grape harvest begins across much of the French vineyard, when orchards are being picked, and when gardeners are trimming hedges that sometimes conceal a nest 60 cm across. The overlap is mechanical, and it explains why accidents cluster in autumn.

Where does the species stand in France in 2026?

Accidentally introduced into the Lot-et-Garonne department around 2004, probably via a consignment of pottery imported from China, the Asian hornet has colonised almost all of mainland France in about twenty years. The Muséum national d'Histoire naturelle, which has monitored the species from the outset through the Inventaire national du patrimoine naturel (INPN), has documented an advance of roughly 60 to 80 km per year towards the north and east.

Today, only a few high-altitude areas and the most continental fringes remain sparsely colonised. The species is classified as an invasive alien species at European level (EU Regulation 1143/2014) and, in France, appears on the list of category two health hazards for the honey bee, a status set by ministerial order since 2012.

The recent legislative turning point: the law of 22 April 2025 on combating Asian hornets, which establishes a national control plan and provides a funding framework bringing together the State, local authorities and the beekeeping sector. In practice, this does not mean nest destruction becomes free everywhere — the arrangements largely fall to departments and municipalities — but the network for reporting and handling cases is becoming more structured.

Key point: the Asian hornet is not a pest subject to a legal obligation of destruction for private individuals. Destroying the nest is not compulsory, but it is strongly recommended when the nest is close to a place where people pass by.

Why the grape harvest concentrates the risk

Ripe grapes are a hornet magnet

A bunch damaged by hail, pecked by a starling or attacked by wasps releases sugary juice. That is a powerful olfactory signal. Asian hornets do not generally pierce intact grape skin, but they exploit already-open berries on a large scale — behaviour well documented by the chambers of agriculture and the IFV (Institut Français de la Vigne et du Vin) in plant health bulletins.

The picker, meanwhile, plunges a hand into the bunch without seeing the insect. This is the leading cause of stings in a vineyard setting: not a defensive attack from a nest, but accidental hand-to-insect contact.

Confusion with the common wasp

In a single plot you will find German wasps, European hornets and Asian hornets side by side. Knowing how to tell them apart changes what you should do:

The most reliable field criterion remains the yellow-tipped legs on an overall dark body. The European hornet, for its part, is effectively protected and thoroughly useful: its nest must not be destroyed by mistake.

The nest hidden in vegetation

Secondary nests are mostly built high up, in trees, often more than 10 metres above the ground. But a significant share — estimated by beekeeping health protection groups at between 10 and 30% depending on the region — sits less than 3 metres up: dense hedges, bramble thickets, garden sheds, under a roof overhang, in a woodpile, or even in a compost bin.

As long as the trees still have their leaves, these nests remain invisible. That is why a hedge trimmer on a telescopic pole triggers serious accidents every autumn: the noise and vibrations are perceived as a direct attack.

What an Asian hornet sting actually does

One myth needs defusing: Asian hornet venom is no more toxic than wasp venom, dose for dose. Published research and ANSES's positions agree on this point. What differs is the volume injected (the sting is longer, the quantity of venom greater) and above all the number of stings possible during a colony attack, since a hornet can sting repeatedly.

Three clinical scenarios, according to the guidance issued by Ameli and Vidal:

• Ordinary local reaction: immediate intense pain, redness, swelling of a few centimetres that subsides within 24 to 48 hours. By far the most common case.
• Extensive local reaction: oedema larger than 10 cm, lasting several days. Impressive but rarely dangerous, except when located in the throat, mouth or eye — which requires an immediate call to the emergency services (15 in France).
• Generalised allergic reaction (anaphylaxis): hives away from the sting site, facial swelling, breathing difficulty, drop in blood pressure, faintness. An absolute medical emergency. It affects roughly 0.3 to 3% of the population according to estimates, and can occur in someone who has previously been stung without any problem.

The deaths recorded in France each year following a hymenopteran sting — on the order of 10 to 20 according to mortality data — are overwhelmingly anaphylactic shocks, not massive envenomations.

What to do after a sting

1. Move away calmly, without sudden movements: hornets release alarm pheromones that summon others.
2. Remove rings and bracelets before swelling sets in.
3. Bring a heat source close (the tip of a cigarette held at a distance, a hairdryer) for a few seconds: the venom is heat-sensitive.
4. Wash with soap and water, then apply cold using a reusable gel pack wrapped in a cloth.
5. Keep the person under observation for at least 30 minutes.

Anyone already diagnosed as allergic must carry their adrenaline auto-injector pen, prescribed by their allergist, at all times — and the harvest team must know where it is. Desensitisation (venom immunotherapy) exists and is highly effective: it should be discussed with an allergist after a generalised reaction.

Protecting yourself in the field: what really works

For grape and fruit pickers

• Gloves: harvesting grapes is incompatible with a bulky glove, but nitrile-coated gardening gloves are often enough to stop the sting reaching the skin on the palm and fingers.
• Long sleeves and light colours: black and dark patterns are perceived as a threat (the colonies' natural predators are dark and hairy).
• No perfume, no strongly fruity deodorant, and no open can of soft drink left among the rows.
• Take a second to look at the bunch before cutting it. This is the one reflex that genuinely halves the number of incidents.
• Keep a sting first-aid kit in the site toolbox, with tweezers, antiseptic and an instant cold pack.

For beekeepers

September is also the month when the Asian hornet does the most damage to apiaries. The mechanism is twofold: direct predation on foragers at the hive entrance, but above all predation stress — the bees stop going out, the colony fails to build up its winter stores and collapses in January or February, often without anyone making the connection.

The levers documented by ITSAP-Institut de l'abeille and beekeeping health groups:

• Hive entrance muzzles and reducers: they do not eliminate predation but reduce stress and allow bees to keep foraging.
• Electric harps: effective locally at heavily pressured apiaries, but expensive and not 100% selective.
• Spring trapping: highly controversial. ANSES has pointed out in its opinions that mass, non-selective trapping destroys large numbers of non-target insects for an uncertain effect on hornet populations. If you do trap, do it in the immediate vicinity of the apiary, in autumn, using selective cone traps whose openings let small insects escape.
• Strengthen weak colonies and carry out feeding at the end of the day.

For gardeners and homeowners

Before any hedge trimming or work at height in September, spend five minutes observing from a distance. Stand about ten metres away and watch: steady insect traffic always following the same flight path signals a nest. Lightweight compact binoculars make this check far more reliable than a rough glance, especially under a roof overhang or inside a dense cypress.

If you have to work near a risk area without being certain, a reinforced anti-hornet suit — at least 6 mm thick over exposed areas, with a face veil — is the only genuinely effective equipment. Standard beekeeping suits do not protect against the Asian hornet's sting: it goes straight through them.

A nest on your property: what to do

What you must never do

• Never go closer than 5 metres to an active nest in September. A mature colony's defence zone extends several metres and the attack is collective.
• Never try to burn it, hose it down, shoot at it or spray it with an over-the-counter insecticide bomb. Each of these methods triggers a mass exit from the colony and fails to reach the brood protected by the envelope.
• Never intervene during the day: some of the workers are out flying and will rebuild a colony elsewhere.

Who to call, and what it costs

The intervention takes place at night or at dusk, when the whole colony is back inside, by injecting an approved biocide directly into the nest via a telescopic pole, ideally followed by removing the nest.

• The fire brigade no longer intervenes for Asian hornet nests at private homes, except where there is an immediate danger to people (a school, a public road, an allergic person trapped).
• The town hall or the community of municipalities: many local authorities have set up partial or full coverage of the cost. This is the first call to make, every time.
• The network of departmental referents (often via the GDS or FREDON) will point you to trained operators.
• A pest control firm (disinsectisation, rodent control, disinfection): depending on the region and the height of the nest, expect between €80 and €150 for a low, accessible nest and €150 to €350 for a high nest requiring a long pole or a cherry picker. Be wary of the €50 quoted over the phone: it hides extra charges.

To compare the cost items of a pest control intervention, our page on indicative intervention prices and our services offering set out what is covered.

Report the nest, even once destroyed

Reporting feeds the national mapping effort and sometimes triggers local financial support. Two channels:

• The national platform frelonasiatique.mnhn.fr (Muséum national d'Histoire naturelle).
• Your municipality's referent or your regional FREDON.

Photograph the insect or the nest before destruction: mistaken identification (European hornet, paper wasp) is common and leads to needless destruction of beneficial species.

And after September?

By late November, colonies die out naturally with the cold. An empty nest is never reoccupied the following year: there is therefore no point — and real danger if you climb — in taking it down in the middle of winter, unless it is unsightly or at risk of falling. The future queens, however, have left to overwinter: each one can found a colony in spring.

That is why the March–April window, for selective local trapping, and monitoring primary nests (the size of a tennis ball, often under a garden shelter or a roof overhang) remain the real preventive lever. A selective hornet trap set for a few weeks around an apiary in spring, and removed as soon as April ends, is a reasonable measure — unlike permanent trapping with a cut-off bottle, which mainly kills butterflies and flies.

To go further on identifying garden hymenopterans, a well-illustrated field insect identification guide prevents many errors and unnecessary interventions.

Key takeaways

• The Asian hornet danger peaks in France in September and October, not in spring.
• The number one cause of stings during the harvest is accidental contact inside a damaged bunch of grapes, not a nest attack.
• The venom is no more toxic than a wasp's: the real danger is allergy and the number of stings.
• Never approach an active nest closer than 5 metres, and never try to destroy it yourself.
• Call your town hall first: financial support exists in many municipalities.
• Report every nest on the Muséum national d'Histoire naturelle platform.

Sources: Muséum national d'Histoire naturelle (INPN, Asian hornet platform), ANSES (opinion on trapping Asian hornets), ITSAP-Institut de l'abeille, Ameli, Vidal, Law no. 2025-380 of 22 April 2025 on combating Asian hornets.