Pine Processionary Moth in Switzerland
By Wespenprofis.ch · Reviewed by:Fachbewilligung Schädlingsbekämpfung VFB-S · Updated: 3 July 2026
At a glance
The pine processionary moth attacks pine trees and is found in Switzerland mainly in the warmer regions such as around Lake Geneva, in Valais and in Ticino. The adult moths fly from May onwards, and the caterpillars build cotton-wool-like nests in the tree crowns. They carry the same hazardous stinging hairs as the oak processionary moth. Keep away from affected trees and call in a professional.
Distribution in Switzerland
The pine processionary moth (Thaumetopoea pityocampa) is a heat-loving species that attacks pine trees above all. In Switzerland its occurrence has so far been concentrated in the milder regions with suitable tree stands, in particular around Lake Geneva, in Valais and in Ticino. Unlike the oak processionary moth, whose adults fly in summer, the adults of the pine processionary moth are already on the wing from May, which shifts the whole development cycle to earlier in the year. As temperatures rise, it cannot be ruled out that the species will extend its range further north and to higher altitudes in the years ahead.
Identification and way of life
The caterpillars live in cotton-wool-like, whitish silk nests that usually hang clearly visible in the crowns of the host trees, rather than on the trunk as is typical of the oak processionary moth. They too leave their nest at night to move to their feeding sites in single file, which is where the shared name processionary comes from. Over time, affected pines show marked needle loss, which makes the nests all the more conspicuous. Where infestation is heavy, entire sections of the crown can be stripped bare, further weakening the tree and leaving it more vulnerable to other pests.
Why caution is needed
The caterpillars of the pine processionary moth carry the same microscopic stinging hairs containing the urticating toxin thaumetopoein as their relatives on oak trees. On contact, or when the hairs are carried on the wind, they can cause a severely itchy skin rash as well as irritation of the eyes and airways. Because the nests often hang within reach in garden trees or along footpaths, the risk of contact in affected areas should not be underestimated.
What you should do
Keep your distance from trees with visible silk nests and tell children not to touch them. Do not attempt to remove or cut down the nest yourself. Instead, report the infestation to a professional (/prozessionsspinner-bekaempfung), who will remove the nest properly in full protective equipment. You will find more on the closely related species on oak trees in our guide Eichenprozessionsspinner.
Frequently asked questions
Where in Switzerland does the pine processionary moth occur?
It is concentrated in the milder climate zones around Lake Geneva, in Valais and in Ticino, where pine trees are common and the winters are mild enough for the species.
How does the pine processionary moth differ from the oak processionary moth?
The pine processionary moth attacks pines, whereas the oak processionary moth specialises in oaks. Its nests also tend to sit in the crown rather than on the trunk, and the adult moths are already on the wing from May.
Are the stinging hairs of the pine processionary caterpillar just as dangerous?
Yes. They contain the same urticating toxin, thaumetopoein, and on contact cause comparable skin irritation as well as eye and respiratory complaints.