For several years, the edges of the trails and the forest areas of TPM have had to face attacks from the pine processionary caterpillar (Thaumetopoea Pityocampa). Many urban and peri-urban private properties are also affected by this phenomenon.
Notice to walkers
Faced with the resurgence of processionary caterpillar nests and during school holidays, the TPM Metropolis is doing everything possible to secure the surroundings of trails in natural areas in order to allow walkers to walk in complete safety.
The development cycle of the processionary caterpillar, although well known, seems to be disrupted in particular due to climate change. The development of the caterpillar is clearly ahead of the classic cycle. For example, processions are sometimes observed since the months of November/December when normally they should only begin at the end of March/beginning of April. The scale of the phenomenon is therefore exceptional not by its intensity but by its duration over time.
A biological fight
Until 2015, the fight against the pine processionary caterpillar could be organized by regulating its population, in particular through aerial spraying of biological products based on Bacillus thuringiensis. These biological treatments carried out in the fall made it possible to maintain populations for several years. of caterpillars below an acceptable threshold.
Since then, all aerial treatments have been prohibited. This change in regulations had been anticipated and the Métropole TPM was thus part of a biological control approach by using pheromone traps to capture male butterflies before reproduction and thus limit the proliferation of processionary caterpillars. This system has been successfully implemented in the forest areas managed by TPM since 2010..
In order to optimize the process, the agents responsible for maintaining and monitoring the beds also carry out manual weeding operations by cutting and burning infested branches located along the edges of paths, tracks and other access routes.
In addition, the installation of tit nest boxes also helps regulate populations of pine processionary caterpillars. These nest boxes can be installed high up at the beginning of autumn (east, south-east or even north-east orientation. The nesting period is from April to June (incubation 13 to 14 days). During brooding a family tits can consume up to 500 caterpillars daily. Around twenty nest boxes are installed on the Salins and Colle Noire sites.
Health risk
The processionary caterpillar represents a health risk for the forest but also for humans (and pets). Indeed, upon leaving the nest, the caterpillar will consume the pine needles located near the latter, which can include almost all of the needles on the tree. Finally, during its development cycle, the caterpillar will develop stinging hairs which can cause allergic reactions such as itching, respiratory and eye problems. Pets such as dogs and cats should not, under any circumstances, come into contact with or ingest the caterpillars.
It is therefore appropriate for forest users to respect certain safety instructions:
- Do not travel on tracks and paths that may be closed to pedestrian traffic due to the proliferation of caterpillars,
- Do not leave marked paths,
- Do not approach branches infested by the caterpillar or on which nests are located,
- Do not touch or crush the caterpillars,
- Keep children away from processions and nests,
- Keep dogs on a leash.
Concerning private owners also affected by this phenomenon, it is recommended that they equip themselves with suitable means of control (self-adhesive strips, reservoir traps) and carry out, or have carried out, the cutting of infested branches by a professional.
If you have to cut infested branches yourself, it is imperative to equip yourself with a full suit, gloves, eye protection (goggles, mask) and respiratory protection ( cartridge mask for example). The branches must be burned in a secure place to prevent the spread of the fire.
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