Host preference, entomopathogenicity, and symbiotic bacterial associates of the nematode, Oscheius carolinensis

The entomopathogenic potential of Oscheius carolinensis (Nematoda: Rhabditidae), a recently described nematode species, was tested on various developmental stages of five insect species. The nematode penetrated, killed, and reproduced in all of the insect species tested; however, some insect developmental stages proved more susceptible to mortality than others. O. carolinensis was consistently associated with three bacteria, one of which, Serratia marcescens, killed fourth-instar Helicoverpa zea larvae within 24 h at concentrations as low as 33 mg/mL. Another species, Enterococcus mundtii, inflicted levels of mortality of 33.3% only after mechanical wounding (pin-pricking) of H. zea and at much higher concentrations. The third species, Achromobacter xylosoxidans, did not cause mortality even at the highest dose tested (500 mg/mL), with or without wounding. The nematode’s host searching behavior and survival strategies conform to those reported for other entomopathogenic nematodes.