Surely you have seen, walking through the parks of Madrid, that some of the trees have ringed bags on their trunks. The text printed on them already warns: “Warning! Danger!”. These bags are installed every year by the Department of Environment and Mobility of the Madrid City Council and the danger they warn about is that of an insect: the pine processionary caterpillar (Thaumetopoea pityocampa).
That surname, “pine”, refers to the type of trees in which they install their pockets (which is what their nests are called), although they can also be present in cedars. During the winter they can be seen on the branches of these trees and, with the arrival of good temperatures, they descend the trunks and form their characteristic processions.
It is at that moment of descent that these bags fulfill their function: that of trapping the caterpillars before they reach the ground to prevent their proliferation in public spaces.
Four types of measures against caterpillars
The installation of bags on trees is the last of the four phases that are carried out each year to remove as many caterpillars as possible. It is sought that at the same time are environmentally friendly and consist of:
- Phase 1: removal of the pine bags. It is carried out between January and February.
- Phase 2: ‘operation pheromone’. Pheromone traps are installed to capture male specimens and prevent the reproduction cycle. It is carried out in summer.
- Phase 3: endotherapy treatment on trees. Authorized phytosanitary products are injected into the leaves through the sap and kill the caterpillars when they eat the leaves. It is carried out in autumn.
- Phase 4: installing perimeter rings around tree trunks. To prevent the caterpillars from descending to the ground and forming processions.
In February of this year, a pilot project was also launched with experimental drone flights to detect the presence of these insects in trees that are difficult to access. If it has good results, it could be used in areas such as El Retiro, Casa de Campo, Capricho, Tres Cantos, La Elipa, San José or Dehesa Boyal.
What to do if I find processionary caterpillars?
It is very important not to touch or step on them as their hairs are very stinging and can cause irritation and allergies to the skin, eyes and mucous membranes. Sometimes it is not even necessary to come into direct contact with the caterpillars, it is enough to be in an area of pine or cedar trees.
This was the case told by this woman in an episode of the podcast La Ruina: a gust of air was enough to transport the stinging hairs, which got stuck in her cornea. She described the sensation she felt in her eye “as if it had caught fire”.
The Madrid City Council recommends the following: “If you come across these dangerous insects, do not approach or handle them and contact the municipal services through the 010 telephone number”.
A real danger for dogs
Humans are not the only ones who can be affected by processionary caterpillars: they are toxic and potentially fatal to dogs. In case your pet comes into contact with them, experts mark this roadmap:
- Notify the nearest veterinary center.
- At home, try to remove as many hairs as possible from the caterpillar, without rubbing. The best way is to wash them off with lukewarm water.
- Go to the emergency veterinary center as soon as possible.
Symptoms may include swelling of the mouth, eyelids, salivation and hyperthermia, among others.