Pine processionary caterpillars: danger to children and dogs

Key rules

• Season: Caterpillars leave the pines in processions from roughly February to April, earlier in the south and on the coast, so keep children and dogs away from pines then.
• Private trees: The owner, or the community of owners for shared gardens, must have nests in its trees treated by authorised professionals.
• Public land: The town hall deals with nests on streets and in parks; report them to it.
• Do not touch: Never touch nests or caterpillars, because the airborne hairs cause rashes, eye and breathing problems.

What to look for

Look for dense, white, silky pouches at the tips of pine branches. They look like cotton wool and are the size of a fist or larger. They are easiest to see in winter.

The caterpillars are hairy and dark, with orange-reddish tufts. They grow to 3–4 cm. In spring they walk head to tail in long single-file lines on the ground or up trunks.

Do not touch nests or caterpillars, even dead ones or old nests. Their tiny hairs float in the air. They cause skin rashes, eye irritation and breathing problems.

When the danger is highest

Caterpillars leave the pines in processions from roughly February to April, earlier in the south and on the coast. Keep children and dogs away from pines then. Higher or colder inland areas can run later.

Before that, the caterpillars hatch in late summer or autumn. They live in the nests through winter and feed on needles at night.

Protect children and dogs

• Avoid walking or playing under pines in season. Keep dogs on a lead and away from lines of caterpillars on the ground.
• Teach children that the "furry lines" are not to be touched.
• Dogs are at real risk. If they sniff or lick a caterpillar, their tongue can swell and the tissue can die. Go to a vet immediately if this happens.
• Do not rub your eyes or skin after being near the trees. Change and wash clothes that may carry hairs.

The "What if" section below covers what to do after contact.

Who removes nests

Streets, parks and town woods: the ayuntamiento (town hall) treats or removes nests, usually through its parks, gardens or environment department, or a contracted firm. You can report a nest to the local police, the environment or parks department, or the town's incident app or phone line. Channels differ by town.

Regional forests and protected areas: the regional forestry or environment service is responsible.

Your own garden: the owner, or the comunidad de propietarios for shared gardens, must have nests in its trees treated by authorised professionals. Do not remove a nest yourself. Town halls can order treatment, fine owners who do not comply, and do the work at the owner's cost.

How control works

Professionals use several methods through the year: insecticide on young larvae in autumn, nest removal in winter, trunk collar traps in late winter, and pheromone traps for adult moths in summer. In city trees, insecticide is sometimes injected into the trunk. The timeline below shows the order.

If you rent or live in a community, tell the landlord or the administrator when you see nests so they can arrange treatment.

Timeline and deadlines

• Caterpillars hatch and build white silk nests in pine tops: late summer or autumn

• Insecticide is applied to young larvae by authorised firms: in autumn

• Nests are removed by trained professionals: in autumn and winter

• Trunk collar traps are fitted to catch descending caterpillars: in late winter

• Adult moths fly and pheromone traps are used: in summer

What to watch out for

• Hairs cause rashes, eye and breathing problems: The caterpillars are hairy, dark with orange-reddish tufts and 3 to 4 cm long when grown. Their tiny hairs float in the air and irritate skin, eyes and lungs, so touching is not even needed. Never touch nests or caterpillars. If a child gets a rash or has trouble breathing or with their eyes, see a doctor or pharmacist.

• Dogs can be badly hurt: A dog that sniffs or licks a caterpillar can suffer tongue necrosis, which is tissue death in the tongue. Keep dogs on a lead away from pines from February to April, and go to a vet at once if your dog touches one.

• Processions on the ground: In spring the caterpillars walk head to tail in long lines on the ground and trunks, where children and dogs can reach them. Keep children and dogs away from pines during this time and report nests to your town hall.

• Owners must treat nests in their trees: If the nest is in your garden or a shared garden, you or the community of owners must have it treated by authorised professionals. The town hall can fine you or do the work at your cost. Hire an authorised pest-control firm and do not remove nests yourself.

What if a child or dog touches a processionary caterpillar?

If a child touches one

Do not rub the area. The tiny hairs break and spread when rubbed, and the reaction gets worse.

• Skin: Take off contaminated clothing carefully. Wash the skin with plenty of lukewarm water and soap. Press sticky tape on the skin and lift it off to remove loose hairs. A cold compress eases the itching. A pharmacist or doctor may advise an antihistamine or corticosteroid cream.
• Eyes: Rinse with plenty of clean water or saline for several minutes, without rubbing. Then see a doctor or an eye specialist.
• Mouth or swallowed hairs: Rinse the mouth. Do not make the child vomit. Get medical care.

Call 112 straight away if the child has trouble breathing, facial swelling or a widespread rash. Call too if a young child has had any contact at all. You can also phone the poison information service on 915 620 420. A child who has had hairs in the eyes or mouth should see a doctor promptly, even if the symptoms look mild.

If a dog touches one

Treat it as a vet emergency and go at once. The tongue can swell and the tissue can die within hours. Call the vet even if the dog seems fine, because delay can mean losing part of the tongue.

On the way, and before you leave if you can:

1. Stop the dog rubbing its mouth with its paws or on the ground.
2. Wear gloves. Do not touch the area with bare hands.
3. Rinse the mouth gently with plenty of lukewarm water. Aim from the side of the mouth outward, so the dog does not swallow the hairs. Do not rub with a cloth.
4. Do not try home remedies.

The vet will usually give corticosteroids, antihistamines and pain relief. Sometimes dead tissue has to be removed.

Afterwards, wash the dog's coat and your own clothes, because hairs can stay on fur and fabric. The same steps apply to cats.

Follow the professional's advice

Whatever the symptoms, do what the doctor, vet or poison information service tells you. They can adjust the treatment to what happened.

Frequently asked questions

Who removes processionary nests from a street or park?

Your town hall is generally responsible for nests on streets, parks and municipal woods. In regional forests and protected areas, the regional forestry or environment department deals with them.

Can I remove a nest from my own tree myself?

No, leave nest removal to authorised professionals, because the hairs are airborne irritants. Protective clothing and approved methods are needed.

What should I do if my dog touches a processionary caterpillar?

Contact a vet straight away if your dog sniffs or licks a caterpillar, because the hairs can cause tongue necrosis. Do not touch the caterpillars or the dog's mouth with bare hands. Avoid pine areas on walks while the processions are on.

When are processionary nests treated?

Nests are removed in autumn and winter, and insecticide is used on young larvae in autumn. Trunk collar traps that catch descending caterpillars go on in late winter. Pheromone traps for adult moths are used in summer.