A pathogenic nonoccluded virus in hemocytes of the navel orangeworm,Amyelois transitella (Pyralidae: Lepidoptera)

A small, nonoccluded virus was isolated from the granular hemocytes (=adipocytes) of moribund larvae of the navel orangeworm, Amyelois transitella, collected from almonds in northern California. The virus was readily transmitted perorally in laboratory tests and was highly pathogenic to neonate larvae; however, third- and fourth-stage larvae usually acquired attenuated infections that retarded growth and delayed mortality. Large paracrystalline viral arrays filled the cytoplasm of granular hemocytes of diseased larvae. Attempts to transmit the virus perorally to larvae of nine other species of moths were unsuccessful. The virus is isometric, about 25 nm in diameter, and contains single-stranded RNA. It has been designated “chronic stunt virus” (CSV) and tentatively assigned to the picorna-like viruses.