Oak processionary moth : Observatree guides

The caterpillars (larvae) of the oak processionary moth (OPM) (Thaumetopoea processionea) can threaten the health of oak trees (Quercus species) by feeding on their leaves. Large populations of the caterpillars cause extensive defoliation of oak trees, leaving them vulnerable to attack by other pests and diseases, and less able to withstand adverse environmental events such as floods and droughts. The caterpillars are also a significant public and animal health risk, as they bear toxic hairs which can cause itching skin rashes, eye and throat irritation and breathing problems. Hence it is important not to approach or touch the caterpillars, or their nests