The increase in the processionary caterpillar pest in Mallorca

A real risk to humans, dogs and cats

The processionary caterpillar - very nasty

Cold weather and heavy rain can help to kill off the caterpillar, but if it's warm and there isn't rain, the caterpillar proliferates. | MDB

Andrew EdePalma07/03/2025 10:25

Luis Núñez, head of the Balearic Forest Health Service, says the climate explains the increase in the number of processionary caterpillars in Mallorca. Each female caterpillar that reaches adulthood lays 200 eggs and the insect is increasing its life expectancy. If a few years ago only four per cent of the caterpillars became butterflies, now between 10 and 15% survive. "This year there are more processionary caterpillars than last year, not only in Mallorca, but also in Extremadura, Murcia, Valencia and Catalonia. There is a climate explanation. It has not been very cold and it has not rained much."

The caterpillar was first detected in 1975. In the Balearics, it is contained only in Ibiza, where not a single pine wood has been defoliated and it isn't considered to be a pest. "What is happening this year," says Nuñez, "is something that we already saw was going to happen. If you look at the maps that we post each year, you can see that it is becoming more widespread. In 2024 there was a lot of damage. If the climate is favourable, we know that the following year there will be more. This is the cycle."

Insecticide spraying is the most effective weapon, but by February or March it's too late. "The butterfly lays its eggs in August. The only authorised insecticide acts on levels one and two larvae, so it must be applied between October and November in order to be effective."

There are the other means of dealing with the caterpillar, such as shooting their nests, but greater effectiveness lies with traps being placed on trees in July and August and with predators. In addition to insectivorous birds and bats, there are other predators, specifically three species of parasitoids. "This is something we have studied with the university. The release of specimens in Formentera has been carried out, and it's working well."

The government and town halls have their respective responsibilities for dealing with the caterpillar, but Nuñez emphasises that individual owners have responsibilities as well. The pine most commonly found in gardens is the Canary Island pine, and it is particularly affected by the caterpillar. "If people have properties where there are children or dogs, the best thing to do is to hire an insecticide-spraying company in October."

Dermatitis, skin lesions, hives and allergies are some of the conditions caused by the pine processionary in humans. The allergic reaction can be very serious for dogs and can even cause death if the tongue and throat swell to the point of obstructing the airways.

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Wildwood | 12 days ago

Last year our valley had many more nests than this year. They seem to alternate on which side of the valley they predominate; last year it was our side, and they were in almost every tree in the lowest terrace. I took out about 6 nests last weekend.

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