Virulence of Anagrapha falcifera nuclear polyhedrosis virus to economically significant lepidoptera

Anagrapha falcifera Nuclear Polyhedrosis Virus (AfNPV) has exceptional comm ercial potential due to its broad host range among Baculoviridae. We compar ed the virulence of AfNPV toward 2nd instar corn earworm, Helicocerpa tea ( Boddie), tobacco budworm, Heliothis virescens (F.), beet armyworm, Spodopte ra exigua (Hubner), fall armyworm, Spodoptera frugiperda (J. E. Smith), and diamondback moth, Plutella xylostella (L.), with homologous and heterologo us baculovirus standards. We also investigated effects of a contaminating c ytoplasmic polyhedrosis virus (CPV), a fluorescent brightener, and genetic selection on the virulence of AfNPV. Based on relative susceptibility to Af NPV, the insect species were ranked (most to least susceptible) as follows: H. virescens > H. tea > S. exigua > S. frugiperda > P. xylostella. Contami nation of AfNPV with naturally occurring CPV did not have a significant eff ect on AfNPV virulence. The virulence of AfNPV and AcNPV (Autographa calfor nica nuclear polyhedrosis virus) toward S. exigua and P, xylostella was not significantly different AfNPV is also as virulent as SeNPV (Spodoptera exi gua nuclear polyhedrosis virus) toward S. exigua. AfNPV was significantly l ess virulent than H. ten nuclear polyhedrosis virus (HzNPV) toward H, tea, but its virulence toward H. virescens was not significantly different from HzNPV. Survival time assays on neonate H. virescens showed that HzNPV kille d significantly faster than AfNPV. The addition of a fluorescent brightener , Blankophor (1%, wt:vol) to the virus inocula significantly enhanced AfNPV virulence toward all 4 species tested, but major gains in potency were rea lized only against S. exigua and P. xylostella. Genetic selection of AfNPV by 10 serial passages through P. xylostella did not significantly improve v irus virulence against P. xylostella. We predict that AfNPV may provide acc eptable control of H. zea, H. virescens, and S. exigua in the held and may also provide control of P. xylostella with the addition of Blankophor.