How to identify a primary Asian hornet nest in April

The April window: why now is the moment

The annual cycle of the Asian hornet (Vespa velutina nigrithorax) follows a calendar of near-military precision. In March-April, a single foundress queen, having emerged from her solitary winter shelter in a protected cavity, begins to build the colony's first nest — known as the primary nest. This nest is initially the size of a walnut, then of an orange. At this stage the queen builds it alone, defends it alone, and lays the first eggs that will produce the first workers.

This temporal window is crucial. Destroying a primary nest in April takes 20 to 30 minutes, costs typically between 150 and 250 €, and prevents the development of a colony that would have numbered several thousand individuals by August. Conversely, destroying a secondary nest in July is an at-height intervention, in full protective dress, with a telescopic pole, often at sundown to minimise worker aggression. Cost: 450 to 1,200 € depending on configuration.

The annual cycle of Vespa velutina

On the French Riviera the species is now well established at every altitude below 1,500 m: Monaco, Cap-d'Ail, Èze, La Turbie, Beausoleil, Roquebrune-Cap-Martin, Mougins, Saint-Paul-de-Vence and Vence are particularly affected. Private gardens on the heights (Tête de Chien, Moneghetti, Jardin Exotique) are favoured sites for primary nests.

The primary nest is typically located in a sheltered spot, at head height: under an eave, in a shed, in a half-open garage, around a window frame, beneath a balcony, in a garden shelter, behind a rarely-opened shutter, in a meter cabinet, in a carport roof, beneath an awning soffit. Proximity to a water source and moderate human activity appears to favour installation.

Where to look for the primary nest

The Asian hornet is recognisable by its black thorax, its abdomen mostly black with a fine orange band at the rear, and its yellow leg tips. It is slightly smaller than our European hornet (Vespa crabro) and almost always darker. It should also be distinguished from the common wasp: the wasp is paler, smaller, and its nest is in open grey papier-mâché.

How to identify without getting closer

In the field, the primary nest of Vespa velutina is easy to recognise: regular spherical shape, walnut-to-orange size, light ochre colour (fresh papier-mâché), small opening pointing downwards, presence of a single queen with calm behaviour — few visible movements. The opposite of a common wasp nest: less regular, greyer, lateral opening, several adults from April onwards.

Why never to attempt it yourself

First absolute rule: do not approach within 5 metres. Even alone, the foundress queen defends her nest with surprising virulence. The sting is no more toxic than that of a wasp for most people, but it is very painful — and several stings can trigger anaphylactic shock in allergic individuals. On the French Riviera, where villas are often surrounded by vegetation, this is the leading cause of incidents.

Second rule: never attempt removal with a broom, a water jet or a domestic insecticide. The broom breaks the nest without killing the queen — who survives and rebuilds elsewhere within a few days. The water jet only disperses. The domestic insecticide is under-dosed and prompts the queen to flee. Worse still: these attempts expose you to multiple stings without neutralising the threat.

Third rule: photograph from a distance and call a Certibiocide-certified professional licensed to intervene. Note the precise location (height, accessibility, presence of children or animals nearby, prevailing wind). Our intervention typically lasts 20 to 30 minutes: securing of the zone, injection of an regulatory-compliant biocide into the heart of the nest with a telescopic pole, removal of the nest at D+7 (to intercept any emerging workers that might have survived).

Our intervention in 4 stages

Vespa velutina is a formidable predator of bees. A developing colony can decimate an entire apiary within weeks, hovering in front of the hives to intercept returning foragers. Destroying a primary nest in April means protecting tens of thousands of foraging bees over the summer. It also means protecting all wild pollinators — bumblebees, hoverflies, solitary bees — whose collapse imperils Mediterranean biodiversity.

The benefit for bees and local biodiversity

Our approach is part of an integrated pest management philosophy. We intervene on confirmed nests, with a minimum effective dose, in a temporal window that maximises impact on the target colony and minimises impact on surrounding beneficial wildlife. All our interventions are documented, traceable, and the applied biocides register is exportable on request by the health authorities.

*Have you spotted a suspect nest in Monaco, on the French Riviera or in the hinterland? Report it to us, we intervene as soon as possible and the April bill bears no comparison to the July one.*

The questions our clients ask most often

How long does the intervention take? On average 90 minutes for an audit plus 2 to 4 hours for a standard treatment in a flat or villa. For complex sites (palaces, restaurants in operation, multi-staircase co-ownerships), the intervention may be spread over several night-time windows to respect your activity. The schedule is always discussed in advance, never imposed.

Is return to occupation fast? For the vast majority of our treatments (bait gel, dry steam, mechanical placement), return is immediate or after 1 to 2 hours of ventilation. For residual regulatory-compliant treatments, we systematically state the recommended interval (typically 2 to 4 hours). For aerosol biocides, the interval extends to 6 hours and we provide a return-to-occupation certificate.

Which legal documents and certificates do you issue after the intervention? After every intervention, you automatically receive in your client area a signed digital report with before/after photos, a treatment certificate admissible for audits, safety commissions and insurers, and an update of the applied biocides register (exportable on request by the French and Monegasque health authorities).

Is there follow-up after the intervention? Yes, systematically. Depending on the service, we schedule a control visit at D+7, D+14 or D+21 according to the biological cycle of the species treated. For 360° monitoring contracts, follow-up is continuous with quarterly reports and immediate intervention on alert from your side.

The cost compared with inaction

An infestation left untreated typically costs ten times more in curative treatment than in preventive arrangements. A few concrete examples from the French Riviera:

• A primary Asian hornet nest destroyed in April: 180-250 €. The same nest as a secondary nest (August): 600-1,200 €. The same colony decimating a neighbouring apiary: beekeeping damage of several thousand euros plus biodiversity impact.
• A palace bedroom closed for 72 hours for bedbug treatment in season: 2,400 € of lost revenue plus reputational damage. The same incident detected in pre-season: 380 € of treatment, zero operational impact.
• A Michelin-starred restaurant kitchen closed for 5 days by a safety commission for cockroaches: more than 100,000 € of lost revenue plus risk of HACCP downgrading. An annual 360° contract: 1,800-3,500 €.
• A co-ownership discovering an advanced capricornes infestation: 15,000-50,000 € in repair works plus curative treatment. A preventive acoustic survey every 5 years: 280 € per visit.

The rule is universal: the audit always costs less than the repair.

Our environmental commitment

All our protocols are designed to minimise the impact on Mediterranean biodiversity. In practice, this means: refusing systematic preventive spraying, selecting biocides with the most favourable environmental profile in their category, favouring mechanical and biological methods where available, respecting non-target species (bees, geckos, hedgehogs, insectivorous birds, bats), keeping an up-to-date exportable register of applied biocides for the authorities.

We also commit to explaining these choices to our clients. Integrated pest management is not a marketing argument — it is a discipline that demands diagnostic time and pedagogy. On sites where a request for "preventive spraying without diagnosis" is made, we systematically propose an alternative: monitoring, audit, targeted treatment on areas of proven risk.

For professionals: regulatory compliance

Our documentation is designed to facilitate the audits of your quality partners. Our intervention reports are compatible with Forbes Travel Guide, Leading Hotels of the World, Relais & Châteaux and Small Luxury Hotels standards in hospitality, and with Bureau Veritas, SGS and ECOCERT audits in catering and the agri-food industry. The biocide register complies with the French order of 28 June 2017 and European Regulation 528/2012.

For charter yachts, our documentation is translated into English and accepted by the main management companies (V.Ships, Bluewater, Y.CO). Contractual NDA is systematic. No establishment, owner or yacht name appears in our external communications.

The culture of premium service

Our technicians come from 5-star hospitality, yachting and prestige hotellerie. This culture of discretion and premium service is our signature. No resident client should ever see a technician in "pest control" uniform. No identifying photograph ever leaves our perimeter. No yacht name, no client name, no identifier appears in our external communications.

This stance is not a commercial argument — it is a contractual obligation for our high-end clientele. And it is the standard we apply to private clients too, because premium service is defined by its consistency, not by its intermittency.

On seasonal dynamics

The life cycle of Vespa velutina strictly follows seasonality: in March-April, the queen alone builds the first nest; in May-June, the first workers emerge; in July-September, the colony reaches its maximum size (often several thousand individuals); and in October-November, future queens leave the nest to overwinter. We recommend that owners and property managers on the French Riviera systematically inspect their properties from mid-March onward — 30 minutes of monthly inspection is enough to spot a primary nest in time.

Commitment to bees

Vespa velutina is one of the main causes of the decline of honey-bee colonies on the French Riviera. An average secondary colony consumes 11 kg of bees over the summer, equivalent to around three beehives. By having a primary nest destroyed on your property, you protect not only your family but also the ecological balance of the entire Riviera. We work regularly with local beekeepers who alert us to activity near their hives — a mutual collaboration we actively encourage.