The major goal of this project is to expand our knowledge about the ecological interactions underlying biological control with beneficial entomopathogenic nematodes (EPNs) to 1) maximize its effectiveness for controlling pest insects and 2) improve public perception and adoption rates. Entomopathogenic nematodes are some of the most promising biological control agents for soil-dwelling insect pests, yet they are still not widely used in U.S. agriculture and represents only a small fraction (about 0.03%) of the U.S. pest control market. The overall objective for our proposed research is to quantify responses of plants to beneficial nematode-produced cues and determine how these responses influence plant interactions with antagonists (i.e., herbivores and pathogens) and mutualists (i.e., beneficial microbes and herbivore natural enemies). We will achieve our overall objective by pursuing three specific aims: 1. Characterize the chemical cues produced by different EPN species with different species of insect hosts. 2. Quantify changes in plant defenses following exposure to EPN-produced cues. 3. Quantify effects of plant exposure to EPN cues on plant resistance to pests and plant recruitment of beneficial organisms. Through this project, we aim to uncover multiple benefits of EPN-based biocontrol to both directly suppress pest insects and indirectly enhance plant resistance to pests. This increased benefit should encourage greater use of EPNs for sustainable pest management.