Outbreaks and Natural Viral Epizootics of the Satin Moth Leucoma Salicis L. (Lepidoptera: Lymantriidae)

Long standing systematic observations on Leucoma salicis populations revealed numerous occurrences of outbreaks and natural viral epizootics. Number of insects appearing in outbreaks at peak density ranged from 450 to 3250 on 10 examined poplar trees (up to 2 m height). Abundance of virus within population of such a high density increased along with an increase of insect population. Populations with high density and high level of nucleopolyhedrovirus (LesaMNPV) and cypovirus did not last long and collapsed suddenly. Outbreaks of the satin moth were favored by warm and humid conditions while warm and dry spring, summer months were conducive to viral epizootic. Most outbreaks happened in the years with mean temperatures of spring and summer months above 15°C and 50-60% RH while, most epizootics were recorded at similar temperature conditions but lower RH, i.e. 40-50%.