Processionary caterpillars in winter

Some reminders

Dangerous for humans and pets

The cause is fine hairs called “mirrors” that caterpillars throw into the air as soon as they feel threatened. These hairs are very stinging.

Dangerous for trees

They feed on needles and when they are very numerous they practically manage to “pluck” a pine tree, which considerably weakens it and makes it sensitive to other parasites.

The life cycle of the pine processionary, Thaumetopoea pityocampa,

Moths fly in July, and females lay eggs during the days.
The eggs hatch one month after laying. It is a little after the hatching that it is advisable to make a treatment with Thuringian bacillus, a specialty that only attacks lepidopteran larvae.
The caterpillars develop in 4 larval stages before burying themselves at the end of winter to transform into a butterfly.
See also on France Bleu Isère:

What struggle during the winter?

– Or remove the accessible cocoons that they form in winter to protect themselves from the cold.
– Either trap the caterpillars at the time of their descent in March.

Why talk about it now?

For weeding:
The earlier it is done in the season, the less itching the caterpillars are.
But each time you have to mutilate the tree to remove these cocoons and in the long run, the crowns of the pines are really degraded.
For trapping:
The traps must imperatively be in place before the start of the migrations which can sometimes begin at the beginning of February.

There is only one type of trap that can be used this season, it is Ecopiège, developed in cooperation between an Occitan startup and INRA, on the market in autumn 2009.
It takes time to take the measurements of the trees to be protected and to order for a positioning during the month of January.

How does it work ?

It is based on the instinct of these caterpillars which move in single file and which, at the end of winter, descend to pupate in the ground. These processions never go up, they always move down. When they encounter an obstacle, the chute of the trap, they will follow it until they find an exit downwards which is a tube leading them into a bag half filled with potting soil where they will bury themselves in groups and in rhythm to pupate.

All you have to do is remove this bag at the end of May, before the butterflies come out and destroy it by fire.
Of course, do not forget to remove the bag otherwise the butterflies can come out and restart the infernal cycle of this parasite.

Installation of the trap:

Detail of parts.

The installer must first prepare the trunk of the tree by choosing a place not easily accessible to the public where the trunk is fairly regular.
It is sometimes necessary to level the bark a little with a “plane” or a wood rasp.
Before ordering, it will have been necessary to measure the circumference of the trunk at the level where the trap will be placed in order to order the corresponding model.
The rest of the installation is well explained on the delivery document and on the site.

Warning

Processionary caterpillars are dangerous for humans and their pets because of their stinging hairs that they can release from their 3rd stage of growth, so particularly when they move in processions.

Outside forest areas, the owners of pines or cedars on which there are regularly processionary caterpillars are civilly and criminally responsible for the accidents that the latter may cause if they have not taken the necessary preventive measures:
-Treatment at the right time Where
-Mechanical weeding
– Descent trapping.

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