The influence of the aphid-specific pathogen Conidiobolus obscurus (Entomophthoromycota: Entomophthorales) on the mortality and fecundity of bamboo aphids

Bioassays and scanning electron microscopy of Conidiobolus obscurus for bamboo aphids as well as its effects on the fecundity of bamboo aphids were carried out to estimate bamboo aphid biocontrol potential. Multi-concentration bioassay and fecundity assessment were performed on aphid species of Takecallis taiwanus, Takecallis arundinariae, Melanaphis bambusae, and Metamacropodaphis bambusisucta. C. obscurus can effectively infect four species of bamboo aphids, and most cadavers appeared in the first 2 days after inoculation. The final mortalities reached 74-91 % at high concentrations of conidia among the tested species. Based on the fitted time-concentration-mortality models, the estimates of the median lethal concentration (LC50) of the fungal conidia differed significantly among different aphid species and decreased with observation days. The lowest LC50 was estimated to be 57 conidia mm(-2) for T. taiwanus on day 5 after conidial shower. Moreover, the C. obscurus-infected aphids only produced 3.9-18.2 % progeny of the corresponding healthy aphids, which strongly presented fungal influence on host fecundity. In conclusion, C. obscurus has the ability of restraining the development of bamboo aphid populations, which is suitable for further application in aphid biocontrol in bamboo forests.