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The oak processionary caterpillar and the forest caterpillar hunter – the story continues

A quiet caterpillar season, an unexpected visit to Jersey and a sequel to the story of the forest caterpillar hunter

Oak processionary caterpillar on the Channel Island of Jersey

Early this year the team was contacted by the Department of the Environment of the Isle of Jersey. Jersey has been struggling with a plague of oak processionary caterpillars for about ten years, and last year also had the first nest of pine processionary caterpillars, the brother of our caterpillar and notorious for its disastrous effect on pine forests. Both species are considered invasive exotic species in Jersey.

Jersey is the largest of the Channel Islands, is a British Crown possession but is close to the Normandy coast. The island has a temperate climate and is intersected by narrow, wooded valleys where pedunculate oaks thrive, ideal for the oak processionary caterpillar.

Dissemination of knowledge, also outside the project area, is part of our duties, so some colleagues went out for a four-day visit at the end of June to view the situation on site and provide advice if possible. We visited a number of locations where nests have been found for years, placed traps to catch parasitic flies and wasps and collected them again, viewed the catch in the on-site lab and brought the interesting species home. We also provided the department with a number of nest boxes that they can use to detect more parasites themselves.

As an extra bonus, they were asked to give a presentation about the project at the ‘Non-Native Invasive Species’ conference in St. Helier, the capital of Jersey. At this conference, local ecologists and experts from Guernsey, Italy, Hawaii, Montserrat and the Flemish INBO discussed the risks of invasive species for biodiversity and public health on the Channel Islands. Our contribution was to provide background information on the possible dangers, distribution and migration trends of both the oak and pine processionary caterpillars.

The forest caterpillar hunter – the story continues

The story of the forest caterpillar hunter has already been covered several times – you could read that in previous newsletters.

It started about when we received several hundred eggs and adults of this beetle species last year from the Turkish General Directorate of Forestry, i.e. the Forestry Commission in Turkey. The species is used there in the fight against the pine processionary caterpillar, a close cousin of our oak processionary caterpillar. Despite the necessary care, these animals turned out to be unsuitable in our fight against the oak processionary caterpillar, so alternatives had to be sought.

Turkey also has populations of the forest caterpillar hunter that have specialized in the oak processionary caterpillar, and we received about a hundred specimens at the end of June. After a long flight from Antalya to Belgium and the necessary checks at the Zaventem Animal Care & Inspection Center, we received the new sprouts. They were immediately taken to the lab in Limburg, where they immediately focused on the collected caterpillars. They are further pampered there and we now hope for many offspring in the coming years!

This year we also intended to visit locations in Flanders and the Netherlands where major doll robbers were reported. In 2022, there were a total of about twenty observations. Unfortunately, the forest caterpillar hunter is apparently also doing less well this year, with only three sightings. That is why those plans have been postponed until the spring of 2024.

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