Every year, they resurface, transforming our gardens, forests and sometimes even urban spaces into veritable danger zones. Processionary caterpillars, harmless-looking little creatures, are a very real danger to humans and animals alike. Urticating, allergenic and destructive to trees, they are spreading at an impressive rate, aided by milder winters and a changing climate. How can we recognize them? What dangers do they represent? And above all, what are the solutions for getting rid of them or limiting their proliferation? Here’s how.
Understanding processionary caterpillars
Who are they and how do they live?
Pine and oak processionary caterpillars belong to the Lepidoptera family. They have a well-established life cycle: they hatch as larvae, go through several stages of development and eventually become moths. But it’s in their caterpillar form that they cause problems.
In winter, they form conspicuous silken nests in trees. As soon as the first rays of spring sunshine appear, they descend in single file, hence the name processionary, to bury themselves in the ground and continue their metamorphosis.
Why are they becoming more and more numerous?
Once confined to certain regions in the south of France, they’ve been gaining ground. Today, they can be found almost everywhere, even in areas where they were rare just 20 years ago.
The main culprit? Global warming. Cooler winters enable them to survive in greater numbers. Add to this the disappearance of some of their natural predators (such as chickadees) and the proliferation of pine plantations, and you’ve got an invasion that’s hard to stop.
Processionary caterpillar risks
A danger to humans
The main problem with processionary caterpillars is their stinging hairs. Invisible to the naked eye, they detach easily and disperse into the air. As a result, the slightest contact can spell disaster.
Symptoms vary from person to person. Some experience simple itching, while others develop real allergic reactions: redness, oedema and breathing difficulties. Worse still, if these hairs reach the eyes, they can cause severe conjunctivitis.
A scourge for animals
If contact is unpleasant for us, it’s much worse for our pets. Dogs, often curious, don’t hesitate to sniff or lick these caterpillars. And then the drama begins.
The tongue can swell to the point of necrosis and, without rapid intervention, the animal can lose part of its tongue, or even die. The same applies to horses and cats, which are not immune.
A significant ecological impact
Forests also suffer. Processionary caterpillars feed on pine needles and oak leaves, weakening trees and making them more vulnerable to disease and other pests.
Solutions to combat the invasion
Best practices to prevent their arrival
Let’s face it: once they’ve settled in, processionary caterpillars are hard to eradicate. So it’s best to act in advance.
Here are a few effective solutions:
- Eliminate nests in winter: if you spot these silky balls in the trees, it’s best to remove them before spring arrives. However, this must be done with care (and ideally by professionals) to avoid dispersing the hairs.
- Install pheromone traps: these devices attract male moths and prevent their reproduction, thus limiting proliferation.
- Encourage natural predators: chickadees, bats and other insects love these caterpillars. Installing bird nesting boxes is an excellent idea.
Natural solutions and treatments
There are also more ecological methods for managing invasions: ecological traps: certain collars installed around trunks capture caterpillars as they descend to bury themselves.
Biological treatments: Bacillus thuringiensis (BT), a bacterium used as a spray, prevents their development without harming other species.
Should I use chemical treatments?
Insecticides do exist, but their use is controversial. Not only can they harm other beneficial insects, but they are not always effective in the long term. In some regions, their use is strictly regulated.
What does the law say?
Given the scale of the problem, some municipalities are now imposing measures to combat processionary caterpillars. Owners of infested trees may be required to take action or face fines.
Conclusion
Processionary caterpillars are more than just a seasonal nuisance. Their proliferation represents a real health and environmental challenge. Fortunately, there are solutions, but they require a collective and coordinated approach.
If you’re faced with this problem, don’t delay. Prevention, natural methods and civic action are the keys to limiting their impact. Above all, stay vigilant, especially if you have children or pets.
So, have you ever come across these infamous caterpillars in procession? How have you dealt with the situation? Share your experience!
