In the Hérault, this invasion of the bombyx which ravages 500 hectares of scrubland on the Causse d’Aumelas

Trees are destroyed by these caterpillars. Scientists are watching.

For miles, the same spectacle of desolation unfolds. On the Causse d’Aumelas and up to the gates of Vendémian, the low scrubland seems to have been exposed to a gigantic fire. Except that at the end of spring, the “fire” which, without distinction, ravaged hundreds of hectares of oaks, holms and kermes, is nothing other than an invasion of a small caterpillar: the one of the disparate bombyx, great lover of oak leaves.

In places, thousands of exuviae litter the ground. “At least 500 hectares of scrubland are affected”, believes Frédéric, owner of the Sainton estate. The winegrower, installed in the heart of the garrigue, has a ringside seat: “Last year, a focus of these caterpillars remained concentrated in a fairly small area, but this is a real disaster…”

Thousands of exuviae litter the ground.

Satellite mapping of the phenomenon

“In the last stages these caterpillars are particularly voracious”, explains Jean-Baptiste Daubree, head of the south-east forest health unit at the regional directorate for Food, Agriculture and Forestry. The scientist is reassuring.

Certainly the butterflies will lay eggs, “and we can count the eggs, but a whole fauna, predators of the bombyx, should settle and reduce the populations”. In the first stage, this non-stinging caterpillar is suspended from a thread which “Allows it to be extremely light and dispersed by the wind. Depending on these currents, it is possible that the phenomenon will disperse”.

The service must also quantify the phenomenon by comparing satellite photographs taken over several months. As for the defoliation, as impressive as it is, it can, under certain conditions, prove to be life-saving. “Normally, most of the trees will ‘leaf again’ at the beginning of July, except in the event of a severe drought. In some cases, such as in 2019, the heat wave was quite severe. And the trees, which had lost their leaves at this time, (paradoxically-NDLR) withstood the heat wave much better than the other trees. Because without leaves, they had no perspiration!”

Still, some trees may not survive these tests if they were to follow one another for several years.

Pupae on holm oaks.

Pupae on holm oaks.

Exuviae: skins rejected by these caterpillars during their moults.

Leave a Comment