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

The browntail moth, Euproctis chrysorrhoea (L.), is periodically a major ur ban pest in the southern United Kingdom. High populations cause severe defo liation of a range of host plants, often in urban areas; and urticating hai rs of larvae are highly irritating to humans. Control of outbreak populatio ns is therefore desired. As an alternative to chemical insecticide sprays a nd labor intensive nest removal, nucleopolyhedrovirus (NPV) has been consid ered as a biological control. To evaluate if use of this spray would affect other lepidopterans we carried out detailed host range testing using a num ber of wild-caught lepidopteran species. Seventy-three species of Lepidopte ra 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 baculov irus 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, uninfecte d control larvae also died of infection, indicating that they carried an ov ert infection in the field. However, in eight species of Lepidoptera and on e sawfly, there were no control deaths, providing possible evidence that an inapparent or latent infection had been stressed out of the wild-caught in sects by inoculation with a high dose of E. chrysorrhoea NPV. Our results s uggest this NPV may be monospecific, and that it is unlikely to present a r isk to ally nontarget species. These characteristics make it highly suitabl e for use as a bioinsecticide, particularly in urban areas and nature reser ves.