faced with the invasion of processionary caterpillars, titmouses called to the rescue

The arrival of spring also marks the arrival of processionary caterpillars, which are developing due to global warming. Some town halls call on titmice to repel them.

Wednesday March 20 is spring! And with it, in the coming weeks, the arrival of oak processionary caterpillars, less known than those of pine but just as problematic. They are also gaining ground because of global warming and are colonizing new departments every year. The Oise, for example, is no longer spared.

Tess moved into her house five years ago, on the edge of the Compiègne forest and its many oaks. Nothing to report until spring 2022. “Everyone had spots, like hives. It’s itchy, it’s huge, like you’ve fallen into nettles,” she describes. Symptoms caused by the stinging hairs of processionary caterpillars scattered in the air.

“It’s not pleasant at all. Plus, we don’t see them, it’s totally volatile.”

Tess, living near Compiègne

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Since then, the insect has been progressing and getting closer to the city. Cocoons were seen in an industrial zone where we find Karine Gelper, director of green heritage in Compiègne. “This is the third year where we have had to face this type of invasion, she observes. The first two years, we intervened curatively, that is to say we came to carry out an organic treatment, as minimally invasive as possible, or even a cutting of the most affected branches. This year’s objective was to find a preventive solution to avoid these treatments.”

“Limit the health risk”

The town hall therefore calls on the titmice, birds that prey on the processionary caterpillar. A family can eat 500 per day, hence the small wooden nest boxes installed on the trees. “Due to the diameter of the orifice, the nest box is rather intended for titmice, she adds. There are around fifteen nest boxes here, in the line of trees. At the foot of the trees, we have shrubs and perennial plants, to provide as much of an environment as possible for the titmouse.”

Useful solution, but not miraculous, comments Anne-Sophie Brinquin. With global warming, there will be more caterpillars anyway, warns this entomology researcher at INRAE ​​(National Research Institute for Agriculture, Food and the Environment). “We will not be able to stop this progression, but the idea will be to limit the health risk, in particular by combining different control methods which target different stages of development of the insect. This is the way we recommend .”

So add to the tits, for example, a bacterial treatment sprayed on the leaves. Once ingested, these bacteria attack the intestines of the caterpillars and get rid of them.