A weevil sex pheromone serves as an attractant for its entomopathogenic nematode predators

Abstract

Diaprepes abbreviatus is an invasive pest of citrus in the USA from the Caribbean. Entomopathogenic nematodes (EPNs) are used as biological control agents in citrus agroecosystems against D. abbreviatus. EPNs respond to herbivore-induced volatiles from citrus roots to assist in the location of insect hosts. Here, we investigated EPN response to the male-produced sex pheromone of D. abbreviatus. In the laboratory, we used two-choice tests to investigate the behavioral response of Steinernema diaprepesi, Heterorhabditis indica, Steinernema riobrave, and the plant parasitic nematode, Tylenchulus semipenetrans, to the synthetic sex pheromone of D. abbreviatus, as well as its natural source, beetle frass. Nematodes were not attracted by volatiles of citrus plant origin or carvacrol, a non-pheromone volatile associated with beetle frass. S. diaprepesi and H. indica were attracted to the frass and the pheromone of D. abbreviatus. The response of S. diaprepesi to the pheromone was greater than that of H. indica at all doses tested; the greatest response from both species occurred at 0.12 and 1.2 ng of pheromone/μL of solvent. Deploying the pheromone in a citrus grove increased the mortality of caged Diaprepes larvae as compared to control larvae deployed with solvent alone. Also, more EPNs were found in the soil surrounding the pheromone-baited larvae than the surrounding controls.