Processionary caterpillar alert in Spain: the pests which can be lethal to pets start to appear four months earlier than usual

The insects’ hairs can also trigger allergic reactions and skin irritation in humans and direct contact with the caterpillar is not even necessary

Ignacio Lillo

Malaga

Tuesday, 22 October 2024, 11:28

Take extra care if you go for a walk in Spain these autumnal days in a forest or leisure areas with pine trees or if you have this species of tree on your property, especially if there are children or pets around. The processionary moth has seen its natural life cycle severely disrupted in some municipalities and those dreaded columns of caterpillars have begun to line up right now, in October, up to four months earlier than normal.

This is the case in municipalities in Malaga province such as Alhaurín de la Torre, where the councillor in charge of environmental matters, Abel Perea, warns that climate change is directly affecting the life cycle of Thaumetopoea pityocampa, to give it its scientific name. "What should normally occur in the months of February and March is taking place in October", he said. This "anomalous behaviour" is related to the high temperatures and the absence of rain until very recently.

The larvae, in their fifth stage of development, move down the trunks of pine trees from their nests in a line, marching nose-to-tail, hence the processionary name. Once on the ground they bury themselves to form the chrysalis that will develop into the adult moth. It is at this time that the caterpillar is most dangerous because its body is coated with stinging hairs that detach and float in the air, causing intense allergic reactions, especially in children and pets.

This phase usually occurs during the months of February and March in our part of the world, although this year it is occurring in October, at least in some places. For this reason, the town's health department is already carrying out treatments to control this pest throughout the year in public parks and calling on the owners of land where there are pine trees to do the same.

Possible causes

Raimundo Real, a zoology professor at the University of Malaga (UMA), confirms that the appearance of these columns of processionary caterpillars in autumn is "rare", as these normally occur at the beginning of spring and into early summer. However, he also emphasised that it has a complex cycle and it is necessary to differentiate between its general phenology (stages in the species' development) and the one it has in this part of Malaga province.

For this reason he believes that it could be a one-off event affecting Alhaurín de la Torre in particular that could be related to the heavy rains in October after a very intense drought. "They haven't come out until now because of the lack of water, because it hasn't rained since March; they have been holding out over the summer and have come out when there has been rain and the temperatures are still not very cold."

However, the professor emphasises that species will always adapt to the circumstances, as "the only thing that does not change in nature is change." He recommends that residents in the affected areas take precautionary measures with children and pets, as they can suffer the worst harm if they touch these insects or even just go near them.

Mild climate and lack of rain

Juan Zamudio, supervisor with Rapiplaga, a Malaga-based company specialising in pest control, is also not surprised that such an early appearance is happening as the mild climate and lack of rain "seriously alters the biology of this and other insects." In fact, he gives as an example the case of the oriental hornet, where the queens should in theory become dormant in winter, but his company is now removing nests "until December and January."

"The fact that it appears 3-4 months earlier than expected is pretty extreme, it completely breaks the biological cycle, which makes it even more dangerous," he said. He advises that all pine trees should be treated at this time to prevent the moths from nesting. "It is as anomalous as it is surprising, and it complicates its control even more." This expert recommends using a biological control, applying the bacterium 'bacillus thuringiensis' to the pines as it is an ecological treatment.

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