INFECTION BY BEAUVERIA-BASSIANA OF LEPTINOTARSA-DECEMLINEATA LARVAE AS A CONSEQUENCE OF FECAL CONTAMINATION OF THE INTEGUMENT FOLLOWING PER-OS INOCULATION

A study of per os inoculated larvae was undertaken to determine if the entomopathogenic fungus, Beauveria bassiana, is able to infect the Colorado potato beetle, Leptinotarsa decemlineata, via the alimentary tract. Surface or per os inoculated larvae which were immediately surface sterilized post inoculation did not succumb to infection, whereas those larvae not sterilized became infected. Histological studies of fed or starved, agnotobiotic (with microbial flora) and axenic larvae revealed that conidia can germinate in the gut regardless of the presence of gut microflora. However, infection via the alimentary tract was never observed in fed larvae and only noted in a single starved individual. It is concluded that infections of per os inoclated larvae occurred after surface contamination of the integument by viable conidia contained in the frass. The rate of food passage through the gut is probably important in preventing per os infections. © 1990 Kluwer Academic Publishers.