Further sightings of processionary caterpillars in France prompt action from local authorities

The early return of poisonous processionary caterpillars in France has prompted local authorities to launch an information campaign as they seek to manage the population. 

The caterpillars are native to France and are spotted during spring, however they are also toxic and can cause fatal injuries to pets, prompting them to be declared a harmful species in 2022.

Named after their tendency to march in single-file line (processions), the caterpillars are covered in minute bristles that detach from their body and can cause irritation, inflammation, and skin rashes in both humans and pets. 

A mild winter with warmer than usual temperatures has led to early sightings, particularly the ‘oak caterpillar’ in the north of France, several months early. 

Not usually present until April, the animals have already been spotted in regions including Brittany and Grand Est.

In comparison, the ‘pine’ caterpillar is spotted in the south between January and May, although is most common in March. 

The animals can be most often spotted on their respective tree trunks, descending from ‘nests’ that resemble balls of cotton wool.

Alert authorities of sightings

The early presence of the caterpillars has prompted local authorities to bring forward awareness campaigns about the animals and begin nest removal where needed.

This includes reminding residents across France of an official open-access website (or smartphone app) that can be used to notify authorities of processionary caterpillars.

You can also call or email your local mairie to inform them of the sighting.

In some regions, such as Brittany, prefectoral decrees state caterpillar sightings must be signalled (although there are no penalties for not doing so). 

As the species are native to France, sightings do not equate to immediate removal of the insects, but are used to monitor their activity within an ecosystem. 

In some cases nests may be destroyed, but only if this is deemed necessary for the local environment or due to local health risks. 

In several communes, this is done through natural measures, including installation of nests for tits (the main predator of processionary caterpillars) nearby or workers manually cutting down nests.

Tree ‘bands’ are also installed where nests are expected, particularly near public parks and schools, to prevent the caterpillars from reaching the ground and harming people nearby.

If you spot the insects in your garden, the official Chenilles-risques website advises to destroy their nests after notifying authorities of their presence.

Nests can be destroyed with the use of traps (purchased at garden centres or through professionals) or promoting the presence of natural predators such as tits.

Chemical solutions are possible – but may harm other species – and cutting down trees where the animals are present is a last resort (and may be prohibited by local regulations).

However, you should be mindful never to touch the caterpillars with bare hands even when they are dead, as the bristles can still irritate. 

If you are concerned about removing the insects, professional gardeners can help.

If you believe you have come into contact with processionary caterpillars, you should avoid rubbing or touching your eyes, and immediately shower once at home. Wash clothes you believe may have been contaminated at 60C. 

When outside near areas where caterpillars are present, wear long clothing to avoid direct contact.

Pet owners warned 

A major concern for residents is the potential fatal nature of processionary caterpillar interactions for pets. 

The irritating bristles of the caterpillars can cause skin rashes and inflammation. 

Ingestion of the bristles can lead to hypersalivation, vomiting, and abdominal pain.

Pets, particularly dogs, find the caterpillars curious and can attempt to paw at or lick them, leading to irritation. 

In the case of the latter, swelling of the tongue can lead to breathing difficulties and severe pain. 

The bristles can also lead to irritation around the eyes of pets and humans, leading to conjunctivitis.

In severe cases, an interaction can be fatal for an animal.

If your pet comes into contact with a processionary caterpillar, you should immediately wash their eyes and mouth and contact a vet.