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Pine Processionary Caterpillars


If you have pine trees, you are probably familiar with the Pine Processionary caterpillar! It is a very pretty caterpillar, brown and black, with a bit of fuzz, but dangerous! When stressed, it releases urticating hairs that can cause injuries to both humans and animals, as well as sometimes severe allergic reactions.


Without any action on your part, it will devastate your pine trees within a few years, leading to their death. So, what can you do? Fight back, of course! The question is, how? First, you need to understand these caterpillars in order to implement an appropriate control strategy.


Processionary caterpillars

Before implementing an action plan, gather information:

Those insects follow a cycle: In early summer, a moth lays its eggs at the top of the pine tree, usually on the south side. The caterpillars devour the needles, and by the end of autumn, they form a large, visible white silk nest. In spring, the caterpillars descend in a procession along the trunk to burrow and form their cocoons. In summer, the moth emerges, living for only one or two days, just enough time to mate and lay eggs.


Nous pouvons maintenant établir des techniques de lutte:

En octobre, Posez des nichoirs avec un orifice de 28 mm de diamètre, cela permettra de sélectionner la mésange charbonnière, grande dévoreuse de chenilles. Les oiseaux ne nichent pas à cette saison, bien entendu, mais quand viendra le printemps, le nouveau nichoir se sera acclimaté et ne « sentira plus le neuf ». La mésange exercera une pression sur la population de chenilles du printemps à l’été.


Now, we can establish control techniques:

In October, place nest boxes with a 28mm diameter entrance hole, which will attract the great tit (Parus major), a major consumer of caterpillars. Birds do not nest during this season, of course, but by the time spring arrives, the new nest box will have acclimated and will no longer "smell new." The great tit will exert pressure on the caterpillar population from spring to summer.


In January, when the large, white silk nests are easily identifiable, they can be removed by cutting the branch that supports them with pruning shears. The nest should then be burned to prevent the spread of urticating hairs. This method is effective but not sufficient, as some nests are too high to reach. However, this technique should be preferred for nests up to a height of 8 meters.


In early March, place eco-traps, collar-like devices that encircle the trunk and collect caterpillars in a bag of soil. This method is also highly effective but not 100% foolproof. The traps can be removed at the end of June.


Ecotrap installed on pine

Early May, set up pheromone traps, one every 25 meters. For maximum effectiveness, the traps should be suspended at a height of 5 meters. The female moth signals to the males by emitting pheromones. The idea is to saturate the area with these pheromones. Male moths either get trapped in the traps or fail to find females, thereby limiting mating.


Even by combining these methods, if the caterpillars are present in your region, it is highly likely that your trees will be reinfested. However, implementing these control techniques will help you maintain your trees in good health without visual impairment.


Another method: You can also seek assistance from a professional who will spray a bacterium on the trees as part of a biological control.


Consider your safety:

Caution! Always wear protective gear before taking action! Opt for plastic clothing that can be rinsed, gloves, and protective eyewear. After the work is done, change your clothes, take a shower without scrubbing vigorously, and shampoo thoroughly.

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