This study examined how differences in the behavioral response of two sod webworm species to Neotyphodium endophytes mediated their susceptibility to an insect-parasitic nematode. In choice and non-choice assays, Parapediasia teterrella (Zincken) clearly preferred endophyte-free tall fescue over endophyte infected tall fescue whereas Fissicrambus mutabilis (Clemens) displayed no clear preference for either. P. teterrella spent more time searching for suitable host material than F. mutabilis and committed to the first host encountered only 37% of the time whereas F. mutabilis did so 90% of the time. Increased foraging times associated with P. teterrella host selection translated into greater rates of infection by the nematode Steinernema carpocapsae (Wieser). Results demonstrate the potential importance of insect behavioral response to fungal endophytes in determining herbivore vulnerability to natural enemies and support the more general idea that insect response to plant defenses may, in part, predict the outcome of insect-natural enemy interactions.