Infectivity studies of a new Baculovirus isolate for the control of the diamonback moth (Plutellidae : Lepidoptera)

This study describes a new baculovirus isolate recovered from infected larv ae of the diamondback moth, Plutella xylostella (L.), and identified as a m ultiple nucleopolyhedrovirus (MNPV). The plaque purified isolate designated as PxMNPVCL3 was found to be pathogenic to P. xylostella, Heliothis viresc ens (F.), Trichoplusia ni (Hubner), H. subflexa (Guenee), Helicoverpa tea ( Boddie),Spodoptera exigua (Hubner), and S. frugiperda (J. E. Smith) larvae in decreasing order of susceptibility. The LC50 for diamondback moth, the m ost susceptible, was 6 occlusion bodies (OB)/cm(2), whereas the most resist ant species, namely S. frugiperda, was 577 OB/cm(2). PxMNPVCL3 was more pat hogenic to diamondback moth by 3-4 log cycles as compared with 2 broad-spec trum baculoviruses, namely Autographa californica (alfalfa looper) MNPV and Anagrapha falcifera (celery looper) MNPV. The 3 baculoviruses were compare d with each other and characterized by restriction endonuclease (REN) analy sis, hybridization, and neutralization tests. Fragmentation profiles genera ted by REN showed that the 3 baculoviruses shared some fragments in common. Hybridization studies employing digoxigenin labeled PxMNPVCL3 DNA as a pro be revealed the close but distinct relationship of these 3 viruses. Neutral ization tests confirmed the hybridization studies, namely that the 3 viruse s although genetically similar are distinguishable from each other.