What stage of *Operophtera brumata* is the overwintering form relevant to dormant oil application management?

The egg stage, laid on bark crevices

Effective, long-term population management for the Winter Moth often targets life stages that are vulnerable and stationary. The physical attributes defined by its classification as a moth dictate that its overwintering phase is spent in the egg stage. These eggs are deposited in crevices on tree bark during the late fall and early winter when the adults are active. This specific knowledge is directly actionable for forest managers; applying dormant oil is a control measure specifically designed to target and smother these overwintering eggs before they can hatch into the damaging larval form in the following spring. This timing targets a physical attribute defined by its taxonomic understanding of its life cycle.