Field experiments were performed to examine how nitrogen fertility mediates trophic interactions involving Neotyphodium fungal endophytes, black cutworm and two biological/biorational controls. Field plots of tall fescue containing either high and low rates of endophyte infection were fertilized using one of three levels of nitrogen fertility (244, 122, 0 kg N/1000sq ft/y. Second 2nd instar black cutworms were caged in eight inch (dia,) PVC cylinders placed within each plot and allowed to feed for 2 days. After 2 d the lids were removed and the grass inside the cylinders was treated with the assigned biological/biorational control agent (Spinosad @ 453ml AI/ha; or Bacillus thuringiensis @ 671g AI/ha). The lids were replaced and the larvae were allowed to feed for an additional 5 d. At 7 d a watering can was used to flush each cylinder with a mixture of water and liquid dishwashing detergent (Lemon Joy™) to disclose the surviving larvae. Larvae were counted and collected into vials of 70% ethanol as they came to the surface. Larvae were then taken back to the laboratory where they were weighed, dried overnight at 80°C, and weighed again. Results and implications of the experiments will be discussed.