In recent years there has been large moth outbreaks in the birch forest west of Vadsø, now the outbreaks have spread to salix shrub and several of the shrub areas east of Vadsø have been completely defoliated.
Photo: Ole Petter Vindstad
In the ongoing population outbreak of winter moth (Operothera brumata)- a species that recently has expanded it outbreak range to the Varanger region - the moth is defoliating large patches of tall willows quite far beyond the arctic tree-line of mountain birch. The winter moth is known to be a more polyfagous species than the native birch moth (Epirrita autumnata). In continental Europe it is a pest species on very different plant hosts - including heather (Caluna vulgaris) and plantations of Sitka Spruce. However, previous outbreaks of winter moth in northern Fennoscandia have primarily been associated with mountain birch, although with sometimes significant spillover to other species of trees and shrubs. That the winter moth now is observed to defoliate, and likely kill, willow shrubs in tundra far from the birch forest indicate that willows alone may sustain outbreak densities of this species. If this is the case, the winter moth may now expand further into the tundra and become crucial actor even in the tall shrub module of COAT.