Integrating endophyte-mediated resistance and biological controls to manage turfgrass insects: Physiological and behavioral considerations

Although endophyte-mediated plant defenses can profoundly influence interactions between insect pests and their natural enemies, efforts to systematically integrate these novel plant defenses into biologically sound insect management strategies are lacking. Our research aims to provide the necessary first step toward developing and deploying plant × endophyte genetic combinations that work in conjunction with biological controls by examining how variation in insect herbivore response to endophyte-mediated defensive compounds influences the effectiveness of the entomopathogenic nematode Steinernema carpocapsae. Our central hypothesis is that the effectiveness of S. carpocapsae will vary with insect response to endophyte-mediated alkaloids; insects that are physiologically adapted to endophyte-mediated defenses may vary in their susceptibility to the nematode when feeding on endophyte infected tall fescue, depending on the degree to which they are physiologically adapted to the toxins (i.e. does the insect simply detoxify defensive compounds or does it actively sequester and remobilize them as a form of defense against its enemies). Conversely, insects that are not physiologically adapted to endophyte-mediated toxins will display a stronger behavioral response, resulting in more movement and potentially greater susceptibility to the nematode.