Characterization of a Novel RNA Virus Discovered in the Autumnal Moth Epirrita autumnata in Sweden

de Miranda, Joachim R.; Hedman, Harald; Onorati, Piero; Stephan, Jörg; Karlberg, Olof; Bylund, Helena; Terenius, Olle

Geometrid moth larvae are major defoliators of deciduous forests in central and northern Europe. In northern Fennoscandia, vast areas of mountain birch forests are recurrently defoliated by larvae of two geometrid species. In colder, continental areas the more cold-tolerant species, the autumnal moth (Epirrita autumnata) dominates while the winter moth (Operophtera brumata) prefers the warmer inland and coastal areas. However, the winter moth has started to appear at outbreak densities in locations where the autumnal moth was previously the sole outbreak species, probably due to climate change [1, 2] . Both species show cyclical population dynamics with regular density fluctuations at cycles of 9-11 years, although the highest seasonal density at any one location and year does not always also correspond to an outbreak density. Winter moth populations show a delayed synchrony, with density peaks lagging one or two years behind the peak densities of the autumnal moth [3] . The cyclic pattern is partly driven by hymenopteran parasitoids attacking larvae and pupae [4] . The major cause of mortality at outbreak densities seems to be starvation. However, occasionally diseased autumnal moth larvae have been observed at outbreak density locations, while no diseased winter moth larvae