People with gardens urged to spot and report this common but dangerous pest via French ministry site

People in France are being urged to report sightings of pine and oak processionary caterpillars via a dedicated government website, in a bid to reduce their number and danger.

Processionary caterpillars are a relatively common sight in France, particularly as temperatures rise. Their nests look like large balls of cotton wool in trees, and the caterpillars themselves can be recognised by their movement in ‘single file’ long lines (‘processions’) along tree trunks and the ground.

They appear in oak and pine trees across 80% of the country.

• Pine caterpillars (chenille processionnaire du pin): Mainly seen in the south, centre and west of France between January and May, with a spike in March. 
• Oak caterpillars (chenille processionnaire du chêne): Mainly found in the north-east, the Paris region and the north-west of France between April and July.

The caterpillars were officially recognised as a harmful species in France in a decree dated April 27, 2022.

Read more: Processionary caterpillars now officially a harmful species in France
Read also: Health warning with France in peak period for dangerous caterpillars 

Toxicity and reactions

The caterpillars are small and ‘fluffy’, but their tiny hairs can cause severe reactions in both humans and pets, and even necrosis of the tongue and mouth if pets lick or eat them. 

They can cause: 

• Skin problems, including redness, itching, skin pain, localised oedema, hives and sometimes small blisters on the skin

• Eye issues, including conjunctivitis, eye watering, pain

• Respiratory problems, including a cough, and breathing difficulties

The hairs can also become detached from the caterpillars and be spread by the wind.

National health agency ANSES states: “The penetration of these stinging hairs into the skin or mucous membranes leads to the release of a venom composed of molecules responsible for toxic reactions.”

Read also: Processionary caterpillars in French forest blamed for sick dogs
Read more: What to do if your pet is hurt by processionary caterpillars in France
Read also: Be aware of caterpillars when walking your dog in France 

Report and fight

Now, the government is urging people to report sightings of the caterpillars and/or their nests via a dedicated website - Signalement Chenilles processionnaires. There is also a smartphone app of the same name.

The service has been created with AtlaSanté, the geographic information portal of the Agences régionales de Santé (ARS) and the Health Ministry, and the caterpillar monitoring service, l’Observatoire des chenilles processionnaires, Fredon France.

Once you have reported the sighting, it is sent to your local commune representative. If they consider there to be a risk to human or animal health, they will coordinate actions to address the infestation.

In case of an emergency (such as someone struggling to breathe), you should still call the emergency services on 15 or 112.

Data collected via the reporting website is also aiming to: 

• Help scientific research on the species

• Map populations more accurately

• Monitor the caterpillars’ evolution in the face of climate change

• Effectively protect public health.

How to avoid a reaction to the caterpillars

To avoid a reaction, people are also advised to: 

• Not approach or touch the caterpillars or their nests

• Stay away from trees with nests 

• Wear long clothing when walking in the forest or near infested trees

• Avoid rubbing your eyes during or after a walk

• Take a shower and wash your clothes above 60°C if you suspect exposure to caterpillars