Pine Processionary Caterpillar Nests: Winter Nest Removal

"We spotted the white balls at the tips of the pine branches in early December. We told ourselves we'd deal with it in the spring. In March, the dog came back inside with a swollen muzzle and we spent the evening at the emergency vet." This homeowner from Ormesson-sur-Marne sums up the classic trap: a pine processionary caterpillar nest is visible in winter, but people wait until spring to deal with it — in other words, exactly the moment it becomes dangerous.

Between November and February, the colonies are concentrated, visible, motionless during the day, and still relatively mildly irritant at the very beginning of winter. It is the most comfortable intervention window of the whole year. Once the end of February has passed, the caterpillars have moulted several times, they are covered in urticating hairs, they come down in single file, and the risk shifts onto children, dogs and cats.

This guide covers a point that spring prevention articles tend to leave out: winter nest removal — what the regulations have required since 2022, the right period, what you can and cannot do yourself, the cost of a professional visit, and above all the question that comes up most often among Val-de-Marne homeowners: the pine tree is on my neighbour's land, what can I demand?

Identifying a winter nest and not mistaking the species

The nest of Thaumetopoea pityocampa, the pine processionary moth, is a pearly white silk bag ranging from the size of a fist to that of a rugby ball, attached to the tip of a branch, generally on the south side, in the upper third of the tree. It is opaque, clearly visible when the rest of the vegetation is dormant, and it holds anything from a few dozen to several hundred caterpillars.

Three common mix-ups:

• The oak processionary nest (Thaumetopoea processionea): it looks nothing like a bag at the end of a branch. It is a silken patch pressed flat against the trunk or a large scaffold limb, shaped like a flattened pouch. It appears in spring, not in winter. If you see a mass of silk on an oak in December, this is not what you're looking at.
• Ermine moth webbing (on hawthorn, spindle, plum): a fine, transparent veil enveloping an entire leafy shoot. No health hazard whatsoever.
• A simple clump of dead needles held together by resin: no dense silk, no black droppings at the bottom.

The giveaway detail: at the foot of an infested pine you'll find clusters of small cylindrical black droppings and chewed needles. And the tree shows branches stripped as if cut with scissors, often asymmetrically.

Across the département, the trees concerned are mainly the Austrian black pines, Scots pines and maritime pines planted in the 1970s to 1990s in housing developments, parks and around schools — but also cedars, which can be attacked too.

Why winter is the right season

The insect's life cycle explains everything. The moths fly in summer, the females lay their eggs in a sleeve around a shoot, the caterpillars hatch in autumn and develop throughout the winter inside their silk nest, coming out at night to feed on needles. When temperatures rise again — typically from late February to April in the Île-de-France region — the colony leaves the tree in procession to bury itself in the soil and pupate.

Hence four arguments for acting now:

1. The nest can be located. In winter, the absence of surrounding foliage and the white colour make spotting with binoculars very easy; in spring, the colony has already left and there is nothing left to treat.
2. The entire population is inside the bag. Removing one nest means eliminating several hundred individuals in a single go.
3. You act before the processions, that is, before the caterpillars reach ground level, where children and pets come across them.
4. You break the cycle before the next egg-laying. Every untreated colony produces moths in July and August, which will recolonise your pine and your neighbours'.

One word of caution all the same: the urticating hairs (the silk contains thaumetopoein) are already present from the third and fourth larval instars, so from mid-winter onwards. "Winter" does not mean "risk-free".

What the regulations have said since 2022

An important point, often poorly understood by homeowners: both processionary caterpillars (pine and oak) were added to the list of plant and animal species harmful to human health by the order of 25 April 2022, issued under decree no. 2022-686 of 25 April 2022 (French Public Health Code, articles L.1338-1 et seq.). The texts can be consulted on Légifrance.

In practice, this framework:

• officially recognises the health risk (dermatitis, conjunctivitis, respiratory problems, anaphylactic shock in sensitised individuals);
• gives the prefect and the mayor the power to prescribe control measures, including on private land;
• allows the mayor, under their general policing powers (article L.2212-2 of the French General Local Authorities Code), to formally order a property owner to have their trees cleared of nests when the presence of nests creates a danger for the neighbourhood, a pavement, a school playground or a play area.

There is no uniform, automatic nationwide obligation to clear nests from every pine tree in France. However, many municipal and prefectoral orders do require nest removal in identified zones. Before taking any action, the sensible first step is to call the hygiene and health department at your town hall to find out whether a local order applies in your commune — the answer changes the whole nature of the case if the problem originates with a neighbour.

And whatever the regulations say, the principle of civil liability still applies: an owner who allows nests to proliferate on their land after having been warned is liable in the event of damage (article 1240 of the French Civil Code).

When the tree belongs to your neighbour

This is the most common scenario in a housing development in Champigny-sur-Marne, Sucy-en-Brie or Villiers-sur-Marne: the big black pine is on the other side of the fence, the nests are clearly visible, and the caterpillars come down into your garden in spring.

The steps to follow, in order:

1. Talk to them, and document everything. Many owners simply have no idea what those white balls are. Photograph the nests from your own property and date the photos.
2. Send an ordinary letter, then a registered letter with acknowledgement of receipt if nothing happens. Mention the health risk, the inclusion of processionary caterpillars on the list of species harmful to human health (order of 25 April 2022) and your request for nest removal before the spring processions.
3. Contact the town hall (hygiene department): if a municipal order exists, the commune can serve formal notice on the owner and, should they fail to act, have the work carried out at their expense.
4. Conciliation officer (conciliateur de justice), free of charge, at the town hall or local court: this is often more effective and faster than legal proceedings.
5. Abnormal neighbourhood nuisance as a last resort, before the judicial court, with your records, medical certificates and vet bills.

You are not entitled to go onto your neighbour's property or to cut their branches, even ones carrying nests. The right to have overhanging branches pruned (article 673 of the French Civil Code) entitles you to require them to cut them, not to do it in their place without agreement. The same logic as for rodents coming in from a neighbouring plot applies, and we have set it out in detail in our guide on rats coming from the street or a neighbouring plot.

Nest removal methods, and their limits

Mechanical removal of the nests

This is the benchmark method in winter. The nest is cut off along with its branch, immediately sealed in a closed bag, then incinerated (never put in the bin, never composted, never crushed on the ground).

Conditions for this to be feasible and safe:

• nest reachable from the ground or from a stable ladder, less than 3 to 4 metres up;
• work carried out in cool, damp weather, early in the morning, with no wind — wind disperses the hairs;
• full protective equipment: disposable hooded coveralls, sealed safety goggles, FFP3 mask, long gauntlets. A telescopic pole pruner keeps you away from the nest and is the basic tool for lower branches;
• never a pressure water jet, never burning the nest on the tree, never shooting it down with a gun (yes, this still happens): all these methods aerosolise the urticating hairs.

Above 4 metres, or for a 15-metre pine in a housing estate, removal becomes work at height for a climbing arborist or a cherry picker: this is no longer a DIY job.

The collar trap (ecotrap)

A sealed collar fitted around the trunk and connected to a bag filled with soil intercepts the caterpillars during their descent procession. This is not nest removal, it is a last-chance barrier: it is fitted at the end of winter, before the descents, and it does not prevent damage to the crown. It remains useful on a tree where nest removal is impossible, provided it is fitted correctly (mastic in every crevice of the bark) and monitored.

Biological treatment with Bacillus thuringiensis

Bacillus thuringiensis var. kurstaki, a bacterium approved for use in organic farming, is sprayed onto the foliage and ingested by the young caterpillars. It is only effective on the first larval instars, so in September and October, not in the middle of winter, and it requires spraying equipment capable of reaching the crown. On a large pine, this is a job for professionals. ANSES publishes the list of authorised products and their conditions of use.

Pheromone traps

Set out in June and July, they capture male moths and serve mainly to measure the pressure from one year to the next. Useful for deciding whether treatment is needed, but insufficient as the sole control measure — the same reasoning we set out for hornet trapping.

Tits

A great tit eats several dozen caterpillars a day, and tit nest boxes placed 3 to 4 metres up, at a rate of one or two per vulnerable tree, are among the recognised levers of population control. It is a long-term complement, to be installed from autumn onwards so that pairs settle in by spring. It does not replace removing an existing nest.

How much nest removal costs

The typical figures seen among Île-de-France contractors, for a detached house:

Several factors move these prices: the height, access (narrow gate, sunken garden), the number of nests, proximity to a school or public road requiring the area to be cordoned off, and the season — in January and February, schedules fill up fast. Our general price ranges are set out on the pricing page and in our article on the cost of a pest control visit.

In case of contact: what to do

The recommended course of action, in line with the guidance issued by poison control centres and relayed by Vidal and the French health insurance service:

• Do not rub, do not scratch: friction breaks the hairs and releases the urticating protein.
• Rinse thoroughly with lukewarm water for several minutes. Rinse the eyes with saline solution, at length, without rubbing.
• Remove the clothes you were wearing, handle them with gloves, and wash them separately at 60 °C. A lint roller for clothing helps lift hairs left on fabrics and car seat covers.
• Call 15 (emergency services) or the poison control centre if there is swelling of the face, lips or tongue, breathing difficulty, or faintness.
• For a dog or cat, head to the vet without delay: contact with the tongue can cause necrosis, sometimes partial amputation of the tongue. Rinse the mouth with water in the meantime, without using your bare fingers.
• After working in the garden, a soothing after-bite gel and a hair wash complete the clean-up.

The winter checklist, out in the garden

• Walk around the garden with a pair of lightweight binoculars and examine the upper third of every pine, on the south side.
• Record and photograph each nest, counting them: two nests on an isolated pine are not handled like twelve.
• Check your neighbour's pines and those along the street — and, if the tree belongs to the commune, report it to the technical services.
• Temporarily move the sandpit, the dog kennel, the trampoline and the pets' water bowl out from under the crown.
• Make your decision before the end of February: after that, the caterpillars come down and the window closes.
• Plan nest boxes for the following autumn and, on at-risk trees, a biological spray in September.

The other seasonal garden jobs often overlap: the same period, the same inspection rounds as for moles, voles and water voles in the vegetable patch.

When to call a professional

Call without hesitation if:

• the nest or nests are more than 3 to 4 metres above the ground;
• the tree overhangs a school playground, a pavement, a play area or a swimming pool;
• you count more than three or four nests on the same plot;
• a member of the household is asthmatic, allergic, or has already had a significant reaction;
• the pine belongs to a neighbour and you need a written report to support your case with the town hall.

We work across the communes of the département: nest spotting, mechanical removal with destruction by incineration, fitting of ecotraps and autumn biological treatment. Full details are on the processionary caterpillar services page, and the list of communes covered on service areas.

A nest spotted in November is dealt with in an hour. The same nest discovered in April means a procession down the garden path, a dog at the vet's and a ruined gardening season. Request a survey via the contact page, or call the emergency line if caterpillars are already on the ground on your property.