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

Authors: RIVERA, MONIQUE - University Of Florida; MARTINI, XAVIER - University Of Florida; Khrimian, Ashot; STELINSKI, LUKASZ - University Of Florida

Submitted to: Chemoecology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/23/2017
Publication Date: 8/30/2017
Citation: Rivera, M.J., Martini, X., Khrimian, A., Stelinski, L. 2017. A weevil sex pheromone serves as an attractant for its entomopathogenic nematode predators. Chemoecology. 27:199-206.

Interpretive Summary: Insect pests cause significant damage to crops and forest, and controlling their populations using natural enemies aids greatly to reducing the pesticide use and biological control. Entomopathogenic nematodes (EPNs) are a group thread worms causing death to insects, including citrus root weevil. Here, we investigated EPN response to the male-produced sex pheromone (or an insect-produced chemical that triggers a natural behavioral response in another member of the same species) of citrus root weevil. Our result showed that certain EPNs are attracted to the synthetic pheromone and use it to locate immature citrus root weevil in the ground. Thus, deploying the pheromone in the field would help to enhance the biological control of citrus root weevil by EPNs. The results of this study are of interest to chemical ecologists and entomologist involved in the research of potential pest control compounds, and to state and federal agencies involved in monitoring and controlling insect pests of agriculture and forest.

Technical Abstract: Diaprepes abbreviatus is an invasive pest of citrus in the United States originating from the Caribbean. Entomopathogenic nematodes (EPNs) are used as biological control agents in the citrus agroecosystems against D. abbreviatus. EPNs respond to herbivore-induced volatiles from citrus roots to assist in location of their host. 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, Heterohabditis indica, Steinernema riobrave, and the plant parasitic nematode, Tylenchulus semipenetrans, to the synthetic sex pheromone of D. abbreviatus, as well as its natural source, the 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. Response of S. diaprepesi to the pheromone was greater than that of H. indica at all doses tested; 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 mortality of caged Diaprepes larvae as compared with control larvae deployed with solvent alone. Also, more EPNs were found in the soil surrounding pheromone-baited larvae than surrounding controls. Our results suggest that EPNs co-occurring with D. abbreviatus use its sex attractant pheromone as an infochemical for host location.