If you have spotted what looks like cotton wool stuffed into pine trees across the Costa Blanca, take note. Those white bundles are usually the nests of Pine Processionary Caterpillars, and they are far from harmless.
Despite their fuzzy appearance, these caterpillars are a genuine health risk, especially for dogs and children. Local vets see cases every year, and dog owners regularly warn each other when the caterpillars start their march.
Why are the Pine Processionary Caterpillars dangerous?
The danger lies in their microscopic urticating hairs. When disturbed, stressed or even brushed against, the caterpillars release thousands of tiny barbed hairs that:
- Trigger severe skin rashes
- Cause intense itching and irritation
- Lead to breathing difficulties if inhaled
- In extreme cases, provoke anaphylactic shock
Even when the Pine Processionary Caterpillar is dead, the hairs remain active and dangerous.
Dogs are particularly vulnerable. They sniff, paw or lick them. Once the hairs reach the tongue, they can cause:
- Sudden swelling of the tongue and mouth
- Excessive drooling
- Vomiting
- Tissue damage
- In severe cases, death if not treated quickly
If you suspect contact, go to a vet immediately. Treatment often involves cortisone and urgent anti inflammatory care.
Pine Processionary Caterpillars: Life cycle in Spain
The pine processionary moth appears between May and July, living only briefly to mate and lay eggs, often up to 300 per female.
After hatching, the Pine Processionary Caterpillars pass through five growth stages. During the third stage, they build the distinctive white silk nests in pine trees. By February to April, they descend in long head to tail lines, the famous “procession”, to bury themselves in the soil and pupate.
This ground procession is when encounters with pets and people are most common.
You can recognise them by their orange brown bodies with blue bands and their habit of moving in a chain.
with blue bands and their habit of moving in a continuous chain.
What pet owners should look out for
The nests
Nests usually appear from December or January, sometimes earlier in mild winters. They look like cotton wool balls, often on the sunny side of pine trees, as warmth helps the larvae develop. They are often the size of a small melon.
Caterpillars leave the nest at night to feed and return before dawn, but they can also descend to the ground in search of food.
If you have pine trees on your property, you may notice the same trees affected year after year.
Removing nests safely
If nests are within reach:
- Spray with insecticide or household bleach
- Or cut the branch using long-handled pruners
Before removal, dampen or spray the nest to reduce airborne hairs. Some people use hairspray first to trap the hairs.
Never handle nests without protection. Wear gloves, mask and eye protection.
Burning is risky, as it can release hairs into the air.
If the nest is too high
Special tree collar traps can be fitted around trunks about two metres from the ground. These force caterpillars into a collection bag as they descend.
The bags are later removed and disposed of safely. The collars can be reused each year.
During the “marching season”
Caterpillars usually begin marching from February or March, sometimes earlier in warm winters. A procession can contain hundreds of caterpillars and stretch several metres long.
They are blind and move nose-to-tail, often in the early morning but sometimes during the day.
Even if you do not have pine trees, they can travel into gardens, climb walls and cross roads searching for soil.
It is a good habit to check outdoor areas before letting pets out.
A simple emergency kit many locals keep
- Bucket
- Brush and pan
- Large can of hairspray
- Bleach
- Gloves, mask and eye protection
Spray the procession heavily with hairspray to trap the hairs, then sweep them into the bucket of bleach.
Never crush them with your feet or hands.
If your pet comes into contact with a Pine Processionary Caterpillar
Signs often include sudden panic, drooling, white spots on the tongue, swelling and distress.
This is a medical emergency.
Rinse the mouth gently with water if possible (without rubbing) and go straight to the vet.
Fast treatment can prevent permanent damage or worse.
