Lorraine Williamson
Springtime in Spain brings warmer temperatures, longer days, and a hidden hazard lurking in pine trees—processionary caterpillars. While they may appear harmless as they move in distinctive single-file lines, these creatures pose a serious threat to humans and animals alike. Their toxic hairs can cause painful reactions, making awareness and prevention crucial at this time of year.
This morning, while walking my dog, I saw a long line of processionary caterpillars crossing the path. They must have travelled a considerable distance as there were no visible cocoons in the surrounding trees. All nearby pines had been treated, yet here they were, continuing their hazardous march.
The life cycle of the processionary caterpillar
The pine processionary caterpillar (Thaumetopoea pityocampa) begins life as eggs laid on pine trees. The larvae hatch and form large silken nests in the branches. During late winter and early spring, they descend in single-file processions to pupate underground. This is when they become a serious danger to both humans and animals.
Why are they dangerous?
Each caterpillar is covered in fine, toxic hairs that can cause severe allergic reactions. Contact can result in skin irritation, respiratory issues, and even anaphylactic shock in extreme cases. Dogs are particularly at risk if they sniff or lick them, often leading to necrosis of the tongue and, in some cases, death.
What to do if your pet comes into contact
If you suspect your pet has been in contact with processionary caterpillars, act quickly. Symptoms include excessive drooling, pawing at the mouth, swelling, vomiting, difficulty breathing, and tongue discoloration. Immediately rinse their mouth and affected areas with warm water, but do not rub, as this can spread the toxins. Contact a vet without delay, as early treatment can prevent serious complications.
What should you do if you have pine trees?
If you have pine trees in your garden, regular inspections are crucial. Professional treatment using pheromone traps, biological insecticides, or tree banding can prevent infestations. Never attempt to remove nests yourself, as disturbing them releases toxic hairs into the air.
What should you do if you see them?
If you encounter a procession of caterpillars, keep children and pets away. Inform local authorities or pest control services so they can deal with them safely.
What not to do
Many so-called solutions do more harm than good. Burning nests releases toxic hairs into the air, creating respiratory hazards. Stamping on the caterpillars or using a leaf blower spreads their hairs, increasing the risk of exposure. Drowning them is also ineffective, as toxins remain active even in water. Another myth is using hairspray to immobilise them. This does not neutralise their toxic hairs and may worsen the risk if they are later disturbed.
How to deal with them properly
The best approach is professional removal. Traps and biological treatments are effective long-term solutions. If found on public land, report sightings to the relevant authorities.
Stay aware and act responsibly
The processionary caterpillar is a serious but manageable threat. By staying informed and following proper procedures, the risks to people, pets, and the environment can be reduced.
Also read: Processionary caterpillars in Spain: Their life cycle and hidden dangers