Technical Abstract: Protection against herbivores and insects in the Neotyphodium-tall fescue grass association is provided by toxic secondary metabolites. Root exudates in this relationship contains both hydrophobic and hydrophilic substances released into the soil that are either stimulatory, inhibitory, or inactive to above and below ground pests. Through previous in vitro nematode bioassay experiments it was revealed that phenolic compounds produced in this fungal-grass association exhibited adverse effects to Pratylenchus scribneri. Current research is presented that has identified several groups of potential allelochemicals from endophyte-infected grasses, plant and fungus produced. The results indicate that there is a behavioral response indicative of a chemosensitivity of the nematode P. scribneri when subjected to a class of phenolic compounds suggesting a means of dissecting plant host response from endophyte induced responses. The behavioral changes of P. scribneri in response to this and other allelochemicals predicts that studies of taxis and kinesis of this and other nematodes species may form the basis for distinguishing and identifying the basic grass response from the fungus induce response.