Pheromones enhance biocontrol efficacy of entomopathogenic nematodes under field conditions

In previous studies, ascaroside pheromones derived from entomopathogenic nematodes (Steinernematidae and Heterorhabditidae) were shown to enhance nematode dispersal and infectivity. In laboratory and greenhouse experiments, pretreating entomopathogenic nematodes with pheromone extracts caused increased biocontrol efficacy against several insect pest targets. However, the impact of pheromone treatment had not yet been tested under field conditions. In a pecan orchard, we tested entomopathogenic nematodes (Steinernema feltiae) with and without pheromones for the ability to control larvae of the pecan weevil, Curculio caryae (Horn) (Coleoptera: Curculionidae). Pecan weevil is an important pest of pecans in the US. Nematodes with and without pheromone treatment reduced pecan weevil survival compared with a non-treated control. However, S. feltiae + pheromone reduced pecan weevil survival more than S. feltiae without pheromones (35% survival compared with 60% survival, respectively). This trial represents the first report of ascaroside pheromones enhancing biocontrol efficacy of entomopathogenic nematodes under field conditions. Additional trials against pecan weevil and other pests will be forthcoming.