Nitrogen fertility interactions between Neotyphodium fungal endophytes, their grass hosts, insect herbivores, and entomopathogenic nematodes

M. Walter Baldauf and Douglas S. Richmond, Department of Entomology, Purdue University, West Lafayette, IN.       

A series of experiments were performed to examine how nitrogen fertility affects interactions between Neotyphodium fungal endophytes, their grass hosts, insect herbivores, and entomopathogenic nematodes.  To asses plant and endophyte performance, sprigs of endophyte-infected and uninfected tall fescue, Lolium arundinaceum (Schreb.), were cultured in sand using 3 different rates of urea-N.  Plants were allowed to grow for 96 days and the number of tillers, above- and below-ground biomass and concentration of endophyte-mediated ergot alkaloids within the plant material were measured and recorded.  To asses insect performance, black cutworms, Agrotis ipsilon Hufnagel, were reared on clippings taken from endophyte-infected and uninfected tall fescue fertilized using the same 3 fertility rates used in the prior experiment.   Larval survival was assessed at 6 and 12 days and final biomass was recorded. In order to asses endophyte and fertility affects on black cutworm susceptibility to entomopathogenic nematodes, these larvae were exposed to Steinernema carpocapsae Weiser in Petri dishes and mortality was recorded every six hours for four days. Mortality due to nematodes was confirmed using White’s traps. Results and implications of the experiments will be discussed.