Overview
- The invasive horse‑chestnut leaf miner has left many urban trees already brown and largely defoliated well before autumn.
- Larvae feed within leaves and sharply cut photosynthesis, triggering early leaf drop and weakening trees for subsequent seasons.
- Officials cite near‑universal infestation in Frankfurt’s roughly 6,400 horse‑chestnuts and note hundreds more affected in Mainz, reflecting nationwide spread since the 1990s.
- Heat and drought have added severe stress and increased susceptibility to bacterial and fungal disease, prompting warnings from conservation groups about long‑term risks to urban chestnuts.
- Recommended control focuses on removing and destroying fallen leaves; insecticides are not authorized for home use, pheromone traps are costly, and natural predators cannot suppress populations reliably.