Monday, December 10, 2007 - 8:29 AM

Influence of nitrogen fertility on endophyte-herbivore-natural enemy interactions

M. Walter Baldauf,, Purdue University, Entomology, 901 W. State Street, West Lafayette, IN and Douglas S. Richmond,, Purdue University, Department of Entomology, 901 W. State Street, West Lafayette, IN.

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.

Species 1: Lepidoptera Noctuidae Agrotis ipsilon (black cutworm)