The pine processionary caterpillar (Thaumetopoea pityocampa) has started appearing in both wooded and urban areas across the Balearics, as is typical from mid-February. Officials from the Department of Agriculture and the Natural Environment expect this year's impact to be comparable to past seasons, although a slight rise in numbers cannot be ruled out. The onset of this species’ season each year poses risks for both humans and pets due to the caterpillar's urticating hairs, which can trigger allergic reactions even upon brief contact.
Present throughout the islands, the distribution of the pine processionary varies by island: it reached Mallorca in 1942, Menorca around 1970, Ibiza by 1975, and was confirmed on Formentera in 2006. The Serra de Tramuntana remains the area with the fewest sightings, according to the CAIB Forestry Service. Following egg-laying in late summer, caterpillars hatch in October, shedding their skin four or five times while building the characteristic nests or ‘bolsones’ in which they reside. Adults descend from the pine trees at the end of winter to burrow into the soil, forming distinctive ‘processions’ during this phase when their hairs are most potent.
David Andreu, spokesperson for the National Association of Environmental Health Companies in the Balearics, notes an increase in the caterpillar’s presence in Eivissa and Formentera in recent years, forecasting a greater impact on these islands. He adds, "It’s important to explain to people how to protect themselves when they spot a caterpillar or a nest under a tree." He also mentions that while this season has started typically, climate change and rising temperatures are affecting the behaviour of certain species, including the processionary caterpillar.
Advice for the public
Children and pets are the most vulnerable groups, as they often play or walk in parks, gardens and wooded areas where the processionary caterpillar descends forming the iconic lines. The general recommendation is to avoid any direct contact with the caterpillars or their nests and to seek immediate medical attention if symptoms arise after possible exposure.
The Palma City Council’s Health Department advises heightened caution from January to March in public green spaces, parks and gardens containing pines. People are encouraged to stay clear not only of the caterpillars themselves but also from the nests and physical barriers installed on tree trunks. Additionally, remaining under pine trees during windy days is discouraged.
Warnings for pets
Dogs, especially puppies, are the most commonly affected pets due to their curious nature. According to veterinarian Manu Ruiz, unlike cats—which tend to avoid the caterpillars even if they roam outside—dogs frequently sniff or bite the insect, coming into contact with its irritating hairs and triggering strong inflammatory reactions. Ruiz explains these reactions are swiftly noticeable: excessive drooling, swelling around the mouth and nose, and potentially the entire face.
In such cases, the recommended first aid is to rinse the affected area with lukewarm water carefully, avoiding contact with the irritants. If washing is not possible or symptoms worsen, immediate veterinary care is essential. Typically, treatment involves anti-inflammatory medications and, depending on the affected area, may require further interventions. The tongue and snout are often the primary zones affected due to the dog's approach to the caterpillar line. Ingesting a caterpillar can cause digestive issues demanding more complex treatment.
Preventative advice includes steering clear of pine forests during this season or, if unavoidable, keeping dogs on a lead and under close supervision.
Control measures in the Balearics
The CAIB Forestry Service implements control strategies designed to keep caterpillar populations at minimal levels. Monitoring maps are produced island-wide to track developments. In Ibiza and Formentera, both aerial and ground treatments using pheromones and nest removals are applied, while Mallorca and Menorca focus on terrestrial actions targeting recreational areas, singular pines and shelters.
Local councils are responsible for controlling the pest in urban forests and gardens due to the associated risks. This week, Palma and Calvia councils have conducted operations within broader pest control and prevention campaigns. Palma carried out preventive treatments last October and November on over 2,400 pines across various city parks and green spaces. February’s work involves nest removal followed by incineration to minimise ground-level caterpillar presence.
Meanwhile, Calvia is launching a new initiative from 17th to 28th February using sound cartridges—a natural, effective method to safely and precisely eliminate processionary nests, according to council sources.