A new multiple embedded nuclear polyhedrosis virus was isolated from a fourth-instar celery looper,Anagrapha falcifera(Kirby) collected from cabbage in central Missouri in May 1985. Characterization and comparison to other multiple embedded nuclear polyhedrosis viruses via restriction endonuclease analysis indicated a unique baculovirus with a molecular weight of 85.6 × 108Daltons. This baculovirus (AfMNPV) was propagated in cabbage looper larvae and tested against a variety of insect species in laboratory bioassays. More than 31 species of Lepidoptera from 10 families demonstrated susceptibility when allowed to feed ad libitum on substrates (artificial or natural) contaminated with occlusion bodies (OB) at 10 or 100 OB/mm2.Helicoverpa(=Heliothis) zeaandH. virescensdid not demonstrate differential susceptibility to AfMNPV (LC50, 0.36 and 0.39 OB/mm2, respectively) as compared to the alfalfa looper,Autographa californica, multiple embedded nuclear polyhedrosis virus (AcMNPV) LC50, 10.3 and 0.45 OB/mm2, respectively). No other currently known natural or genetically engineered baculovirus infects as many cosmopolitan, economically important insect species or causes mortality as quickly at low concentrations. This is the first baculovirus patented by the U.S. Government Patent and Trademark Office (no. 4,911,913, issued 27 March 1990).