The Pine Processionary Caterpillar: How to Keep Your Garden Safe for Kids and Pets
The pine processionary caterpillar is one of the most notorious — and dangerous — pests that can invade gardens with pines and other conifers. While usually associated with forested areas, they frequently make their way into private backyards, public parks, and residential neighborhoods, posing a risk to people and, especially, to children and pets.
If you have pine trees on your property, staying one step ahead is vital to prevent serious incidents. Below, we break down everything you need to know to protect your home.
1) What is the pine processionary, and why is it dangerous?
The processionary caterpillar is the larval stage of a night-flying moth that lays its eggs primarily in pine trees. After hatching, the larvae weave characteristic white, silken nests in the tree canopy, where they stay sheltered throughout the winter.
As winter wanes and early spring temperatures rise, these caterpillars make their way down the trunks to burrow into the ground and continue their life cycle — this descent is the moment of highest risk for direct contact.
Their appearance is closely linked to the presence of nearby pines or conifers. Mild temperatures, a lack of preventive pest control, or proximity to woodland areas all encourage their spread.
The “processionary” gets its name from its unique way of traveling: moving head-to-tail in long, single-file lines, much like a procession. However, their appearance isn’t the main concern.
The thousands of urticating (stinging) hairs covering their bodies can cause skin irritation, allergic reactions, dermatitis, respiratory and eye problems, and even severe lesions or tissue necrosis in the mucous membranes of dogs and cats. The danger spikes when the caterpillars leave the trees and cross the ground, putting kids and curious pets right in their path. For this reason, they should never be handled directly or removed without the proper safety measures.
2) Symptoms and what to do if your dog or cat touches one
Dogs are the most frequent victims of the pine processionary, as they tend to sniff or try to pick up the caterpillars with their mouths during walks or backyard playtime.
The most common symptoms include:
- Excessive drooling (hypersalivation).
- Swelling of the tongue, lips, snout or face.
- Intense pain.
- Vomiting.
- Difficulty breathing.
- Partial necrosis of the tongue in severe cases.
- Extreme restlessness and compulsive scratching at the muzzle.
Cats can also be severely affected, though it’s less common thanks to their naturally cautious behavior.
If you suspect your pet has come into contact with a processionary caterpillar, you must act fast. Here are the immediate steps to take:
- Do not directly touch the affected area.
- Do not rub the animal’s mouth or skin.
- Flush the area gently with copious amounts of water, avoiding any pressure.
- Rush to a vet immediately to get the appropriate treatment.
3) How to identify a processionary caterpillar and tell it apart from other species
The main giveaway — and the best way to avoid confusing it with harmless species — is its signature travel style: marching in a tight “conga line” (a procession), one right behind the other. You’ll spot this behavior mostly in late winter and early spring, as they head down from the trees to burrow into the ground.
Looks-wise, the processionary is about 1 to 1.5 inches (3–4 cm) long and covered in a thick coat of brown, gray and orange-tinted hairs.
Location is another major clue. The pine processionary lives almost exclusively in pines, conifers and, occasionally, cedars, where it builds distinct white silken nests visible in the tree canopy during winter. Other caterpillar species tend to feed on a wider variety of trees and shrubs and do not build these highly recognizable, tent-like nests.
4) What to do if you find one in your garden
Catching an infestation before the caterpillars ever leave the tree is the most effective way to minimize risk. During the fall and winter months, inspect your tree canopies for those telltale white silken nests.
These nests are usually spun on the sunniest branches and look like thick spider webs or clumps of cotton. If you spot these nests in your garden, the colony is already active and will march down the trunk as soon as the weather warms up.
If you find these caterpillars on the ground or nests in your trees, do not try to knock the nests down with household tools or burn them, as this can release the stinging hairs into the air and increase the risk of exposure. Don’t step on or sweep up the caterpillars either: crushing them releases the toxic hairs into the air and soil, multiplying the hazard.
Contact professional landscapers or pest control experts. A professional intervention assesses the scale of the infestation and applies the safest, most effective method based on the season and the health of your trees.
At Ibiza Green, we handle the safe removal of processionary nests and apply preventive treatments like trunk injection (endotherapy), safeguarding your outdoor space without harming your garden’s natural ecosystem. Get in touch with us today!
