Narrow host range nucleopolyhedrovirus for control of the browntail moth (Lepidoptera: Lymantriidae)

The browntail moth, Euproctis chrysorrhoea (L.), is periodically a major urban pest in the southern United Kingdom. High populations cause severe defoliation of a range of host plants, often in urban areas; and urticating hairs of larvae are highly irritating to humans. Control of outbreak populations is therefore desired. As an alternative to chemical insecticide sprays and labor intensive nest removal, nucleopolyhedrovirus (NPV) has been considered as a biological control. To evaluate if use of this spray would affect other lepidopterans we carried out detailed host range testing using a number of wild-caught lepidopteran species. Seventy-three species of Lepidoptera from 14 families, including four species of Lymantriidae and two species of hymenopteran sawfly, were found to be nonpermissive to E. chrysorrhoea NPV at a dose of 10(6) occlusion bodies per second instar. Some individuals from 11 species of Lepidoptera and one hymenopteran sawfly died of baculovirus infection, but none of these were shown, by dot blot analysis of DNA, to be infected with E. chrysorrhoea NPV. In two of these species, uninfected control larvae also died of infection, indicating that they carried an overt infection in the field. However, in eight species of Lepidoptera and one sawfly, there were no control deaths, providing possible evidence that an inapparent or latent infection had been stressed out of the wild-caught insects by inoculation with a high dose of E. chrysorrhoea NPV. Our results suggest this NPV may be monospecific, and that it is unlikely to present a risk to ally nontarget species. These characteristics make it highly suitable for use as a bioinsecticide, particularly in urban areas and nature reserves.