Differential response of a local population of entomopathogenic nematodes to non-native herbivore induced plant volatiles (HIPV) in the laboratory and field

Authors: RIVERA, MONIQUE - Rutgers University; RODRIGUEZ-SAONA, CESAR - Rutgers University; Alborn, Hans; KOPPENHOFER, ALBRECHT - Rutgers University

Submitted to: Journal of Chemical Ecology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/21/2016
Publication Date: 12/19/2016
Citation: Rivera, M.J., Rodriguez-Saona, C., Alborn, H.T., Koppenhofer, A.M. 2016. Differential response of a local population of entomopathogenic nematodes to non-native herbivore induced plant volatiles (HIPV) in the laboratory and field. Journal of Chemical Ecology. 42:1259-1264.

Interpretive Summary: Recent work has shown the potential for enhanced efficacy of entomopathogenic nematodes (EPN) through their attraction to herbivore induced plant volatiles and it has been suggested that some of these volatiles (e.g. pregeijerene and (E)-ß-caryophyllene) might be utilized to enhance EPN attraction in general. However, there has been little investigation into utilizing this or other attractants in systems other than in those in which the compounds were identified. In laboratory six arm olfactory assays a scientist at the chemistry group, USDA, ARS, CMAVE in Gainesville Florida in collaboration with scientists at Rutgers University found a local highbush blueberry strain of the EPN, Steinernema glaseri, to be more attracted to (E)-ß-caryophyllene than to pregeijerene. This was contrary to earlier tests where pregeijerene appeared to be more attractive. In field assays, set up to mimic the olactometer assays, none of the volatile compounds increased attractiveness to, or infection of, caged Galleria mellonella larvae but rather that endemic S. glaseri were more attracted to un-baited than baited cages with G. mellonella larvae. These results indicates, that as has been shown above ground with beneficial parasitoids, that also below ground beneficial IPM organisms, such as EPNs rely on host specific or host related signals and that generic attractants might be of limited value in an agricultural setting.

Technical Abstract: Recent work has shown the potential for enhanced efficacy of entomopathogenic nematodes (EPN) through their attraction to herbivore induced plant volatiles. However, there has been little investigation into the utilization of these attractants in systems other than in those in which the compounds were identified. We compared (E)-ß-caryophyllene and pregeijerene in the highbush blueberry (Vaccinium corymbosum) agroecosystem in their ability to enhance the attractiveness and efficacy of EPN against the system’s herbivore, oriental beetle (Anomala orientalis). Using the local strain of EPN, Steinernema glaseri, in a six-arm olfactometer, the relative attractiveness of (E)-ß-caryophyllene and pregeijerene was tested in the lab to gather baseline values of attraction to the chemicals alone in sand substrate before field tests. The soil of 30 field plants was pre-sampled and baited with Galleria mellonella larvae to select plants with the highest EPN activity. An arrangement similar to the six-arm olfactometer was used in the field by placing the six cages with assigned treatments and insect larvae with and without compound into the soil around the base of 10 plants. The cages were removed after 72 hours and insect baits retrieved and assessed for EPN infection. The lab results indicate that in sand alone (E)-ß-caryophyllene is significantly more attractive than pregeijerene to endemic S. glaseri. Conversely, there was no difference in attractiveness or efficacy in the field study but rather, endemic S. glaseri were more attracted to cages with G. mellonella larvae, no larvae, and cages with the blank control and G. mellonella larvae.