Pine Processionary Caterpillars in the Algarve

What Every Property Owner Needs to Know Right Now

By AlgarVilla Care

If you own a property in the Algarve with pine trees nearby, chances are you have seen them: long, single-file processions of caterpillars winding across the ground in late winter and early spring. These are pine processionary caterpillars (Thaumetopoea pityocampa), and right now — from late February through April — is peak season for their infamous marching behaviour.

While they are a remarkable spectacle of nature, they also pose real health and safety risks to humans, pets, and trees. As your property management partner, we want to make sure you and your guests are informed and protected.

What Are Pine Processionary Caterpillars?

The pine processionary caterpillar is the larval stage of a moth native to southern Europe and the Mediterranean. In the Algarve, you will recognise their presence by:

• White, cotton-like silk nests high up in pine trees, particularly visible in winter when the trees have less foliage.

• Single-file processions on the ground in late winter — caterpillars linked nose-to-tail, often stretching several metres long.

• Extensive defoliation of pine trees, leaving branches bare and weakened.

The Danger: Microscopic Hairs That Sting

The caterpillars are covered in tiny barbed hairs (setae) that contain a powerful protein called thaumetopoein. These hairs are designed as a defence mechanism and can cause serious reactions on contact.

⚠  Health Alert

In humans, contact with the hairs can cause intense skin rashes and itching, allergic reactions including swelling and respiratory distress, and serious eye inflammation. In dogs and cats, contact with the tongue or nose — which often happens when the animal sniffs or licks the caterpillars — can cause rapid and severe swelling, tissue necrosis, and in extreme cases, loss of part of the tongue. Veterinary attention is required immediately.

Protecting Yourself, Your Guests, and Your Pets

Around the Garden

• Never touch or approach a caterpillar procession. 

• Do not let children play near pine trees if nests are visible overhead.

• Wear gloves and long sleeves if working near pine trees.

• Never attempt to remove or burn nests yourself — this releases the hairs into the air and is extremely dangerous.

For Dog and Cat Owners

• Keep dogs on a lead in areas with pine trees during the procession season (February to April).

• If your dog or cat shows sudden drooling, pawing at the mouth, or swelling of the face or tongue after being near pine trees, go to the vet immediately — this is a medical emergency.

• Do not wait to see if symptoms resolve on their own.

Protecting Your Pine Trees

Beyond the health risks, processionary caterpillars can cause lasting damage to pine trees. Heavy infestations weaken trees significantly, making them vulnerable to other pests and disease. Repeated defoliation over several seasons can kill a tree.

Professional treatments include:

• Pheromone traps: Installed on trunks to disrupt the moth's reproduction cycle.

• Biological insecticide (Bacillus thuringiensis): An environmentally safe treatment sprayed on the tree during larval development in autumn.

• Professional nest removal: Carried out by a licensed pest control company using specialist protective equipment.

Seasonal Calendar: When to Act

Autumn (Oct–Dec): Moths lay eggs. Larvae hatch and begin feeding. Best time to apply Bacillus thuringiensis treatment and install pheromone traps.

Winter (Jan–Feb): Caterpillars are in their nests, still feeding. Nests are clearly visible. Professional nest removal can be carried out now.

Late Winter–Spring (Feb–Apr) ⚠: Peak procession season. Caterpillars descend from trees and march in columns to bury themselves in the soil and pupate. Highest risk period for humans and pets.

Summer (Jun–Aug): Adult moths emerge from the ground and fly to lay eggs in pine trees. Cycle begins again.

How AlgarVilla Care Can Help

If your property has pine trees and you are not based in the Algarve full-time, it can be difficult to monitor and respond to this seasonal issue. As part of our property management service, we can:

• Inspect your trees and property for nests and procession activity during routine visits.

• Coordinate with trusted local pest control professionals for safe nest removal and treatment.

• Liaise with your garden maintenance team to ensure preventive measures — such as pheromone traps and early nest monitoring — are incorporated into the seasonal maintenance plan.

• Alert you promptly if we observe significant caterpillar activity at your property.

• Advise incoming guests about safety precautions during the procession season.

The pine processionary caterpillar is one of the most distinctive seasonal realities of living in and around the pine forests of southern Portugal. With the right awareness and timely action, the risks to your property, your family, and your guests can be effectively managed.

If you have any concerns about your property this season, do not hesitate to get in touch with us. We are always here to help.

Know a fellow Algarve property owner who might need this? Share this article — it could save their dog a trip to the vet. 

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