Overview
- Local authorities reported a wide increase in caterpillar nests across municipalities in late June and are actively marking and removing nests at prioritized public sites such as schools, pools and sports fields.
- The caterpillars carry microscopic toxic 'brennhaare' that can cause skin rashes, eye irritation and asthma‑like breathing problems, and officials warn the hairs can become airborne and affect humans and pets.
- Toxic hairs remain in abandoned nests and the environment for years, so health risks can persist after the caterpillars pupate and some local efforts now include repeated checks of treated trees.
- Cities rely on specialist firms that mechanically vacuum and remove nests because chemical treatments are not widely used and municipal budgets and staff do not allow every oak to be treated.
- Longer‑term experiments and planning are under way, including installing nesting boxes for tits that eat the caterpillars, targeted aerial measures in some regions, and preparing next‑season response plans.