The presence of processionary caterpillars has increased in Vitoria-Gasteiz gardens, causing concern among dog owners. This type of caterpillar, known for moving in single file and forming cocoons at the top of pine trees, is hazardous upon contact, as it can cause urticaria.

In response to this situation, some dog owners have put up handmade signs to warn of the danger. For instance, in the garden on Etxezaharra street, opposite the Ariznabarra football field, messages like "Danger. Processionary, leash your dog" can be seen. This green area is popular for dog walking, used by residents from both the local neighborhood and San Martín.

Rows of caterpillars have been observed for weeks in the gardens of Ariznabarra and Olarizu, as well as in other pine forests in Álava. With the arrival of spring warmth, they descend from the trees to the ground. Once on the ground, they are particularly dangerous if touched, especially for dogs, who can develop rashes on their snouts if they try to sniff them. The caterpillars' hairs contain a venom that affects the skin and causes urticaria. Therefore, it is advisable not to let dogs roam freely near pine forests.

To combat this pest, the Vitoria-Gasteiz City Council employs trap bags placed on pine tree trunks. These bags contain pheromones designed to attract male caterpillars after they have undergone metamorphosis. The primary goal is to capture the caterpillars as they descend the trunk. These traps feature a black sheet coated with contact adhesive to deter the processionary from climbing, forcing the caterpillars down a tube into a bag where they are retained.