Dutch expert: Oak processionary caterpillars may survive underground for years

A Dutch biologist warns that oak processionary caterpillars, known as “the larva from hell,” can survive underground in dormancy for possibly several years, making complete eradication unlikely.

Arnold van Vliet of Wageningen University told DR News that while Denmark currently faces an outbreak, Holland has contended with the pests for years. A major infestation in 2019 caused widespread skin and eye irritation across the country, he said.

After a period of low numbers, Holland is now seeing a “marked, strong increase” in caterpillars this year, particularly where trees are heavily infested. Van Vliet stressed that the pests must be managed rather than eliminated, especially in areas where they threaten human and animal health.

Climate change improves survival conditions for the larvae at northern latitudes. Van Vliet noted they can burrow into the soil and remain inactive—possibly for years—before re-emerging in large numbers.

He recommended two control methods: early monitoring to target newly hatched larvae with biological agents and nematodes in spring, and supporting natural predators like tits and other birds that feed on the caterpillars. Once the larvae develop stinging hairs, professional vacuum removal is the only safe option, he warned.