Large quantities of insecticides are used on warm season turfgrasses to combat pest infestations. To investigate the potential for microbial control, we screened commercially available entomopathogenic nematode products against Herpetogramma phaeopteralis Guenée, an economically injurious pest in the south-eastern United States and Caribbean islands. All tested products, based on Steinernema carpocapsae, S. feltiae, Heterorhabditis bacteriophora, H. megidis and H. indica, were pathogenic to H. phaeopteralis larvae in the laboratory, but S. carpocapsae caused the highest mortality. Amongst nematode species, median lethal concentration (LC50) was not different for three different larval sizes (based on 95% CL) with the exception of H. indica, which had higher LC50 for small larvae. The number of infective juvenile stages (IJs) produced per White trap was significantly greater from larvae infected by H. bacteriophora and least for those infected by H. indica. A proprietary formulation of S. carpocapsae ‘Millenium®’ was chosen for further greenhouse experiments. Overall, the neonicotinoid insecticide clothianidin provided the best control, but greenhouse experiments also revealed that the label rate of Millenium (106 IJ/l at 2500 l/ha) reduced webworm populations by 83–93% and was as effective as clothianidin against larger-size larvae. Our data suggest that commercial formulations of S. carpocapsae can be a good option for H. phaeopteralis biocontrol, but further field studies are warranted to confirm effectiveness under different environmental scenarios.