Processionary caterpillars

Processionary caterpillars, take care when coming across them!

Especially children and animals

The processionary or pine caterpillar (Thaumetopoea pityocampa Schiff) is the main defoliating insect of pines and cedars in Portugal and its name comes from the fact that it constitutes long processions of caterpillars that go from the trees to the ground.

In an urban environment, this insect requires constant surveillance and urgent and timely means to combat them given the consequences it can bring in terms of public health.

Your municipality can be the place to warn of the existence of nests and thus start the fight against them. Contact it, search their social media (Facebook page, etc) to find who to contact. It will probably be the Departamento do Ambiente.

A quick Google search gives some links with ideas about traps and mechanical devices to capture the caterpillars. Mechanical destruction of the caterpillars is, at this stage, the most effective method to use.

Try to catch them as they come down the trunk by taping them, over a length of 0.50 m to 1 m, with plastic or paper soaked on both sides with odourless polybutadiene-based glue. The caterpillars will be glued there, but this method is not 100% effective because the first caterpillars are retained but the following ones can go over them and continue the descent.

Also, an adjustable to the tree trunk trap and wide gutter facilitates the descent of the caterpillars into the trap.

The descent of the caterpillars in procession takes a long time, and they can remain in the gutter for several days. Do not touch them or try to hasten their progress. The trap must be kept in place until the end of the processional season.

If necessary, move the trap to a height where the trunk is more homogeneous or trim the bark slightly to adjust it. And place it at a height that neither children nor animals can reach it.

When handling removal of the trap, protect the face, eyes and hands with gloves, goggles and appropriate clothing for the purpose.

 Article by Safe Communities Portugal – more information at