Infection byBeauveria bassiana ofLeptinotarsa decemlineata larvae as a consequence of fecal contamination of the integument followingper os inoculation

Abstract

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 inoculated 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.Abbreviations: CFU: colony forming units, SDAY: Sabouraud dextrose agar plus 2~o yeast extract, SDAY + G: SDAY plus 0.2~o gentamycin sulphate, SWT: sterile water with 0.5~o Tween 80.

Effect of exposure method to Beauveria bassiana and conidia concentration on mortality, mycosis, and sporulation in cadavers of Chilo partellus (Lepidoptera: Pyralidae)

“…Moreover, larvae feeding on treated-leaves may acquire infection via the gut. Allee et al (1990) found penetration of B. bassiana conidia through the gut in larvae of CPB after consumption of treated-leaves. Miranpuri and Khachatourians (1991) found abundantly germinated B. bassiana conidia in the gut of the larvae of the mosquito Aedes aegypti after 24-48 h of exposure.…”

Effects of Bacillus thuringiensis toxin Cry1Ac and Beauveria bassiana on Asiatic corn borer (Lepidoptera: Crambidae)

“…The results reported by Lewis et al (1996) and Wright and Ramos (2005) might be explained by the common fact that larvae feeding on B. bassiana treated leaves may acquire infection via the gut. Allee et al (1990) found penetration of B. bassiana conidia through the gut in larvae of Colorado potato beetle after consumption of treated leaves. Miranpuri and Khachatourians (1991) found abundantly germinated B. bassiana conidia in the gut of the larvae of the mosquito Aedes aegyptii after 24-48 h of exposure.…”

Defense mechanism of the termite, Coptotermes formosanus Shiraki, to entomopathogenic fungi

“…Allee et al (1990) reported that the rapid rate of food passage by Leptinotarsa decemlineata conferred protection against gut invasion by ingested B. bassiana conidia. In addition to the rapid passage of conidia, the microorganisms associated with the termite gut have an inhibitory effect on entomopathogenic fungi ; therefore, it is unlikely that entomopathogenic fungi invade the alimentary tract of the termite, but the fate of the ingested conidia remains to be clarified by further research.…”