Heterorhabditis sp. not attracted to synthetic (E)-β-caryophyllene, a volatile emitted by roots upon feeding by corn rootworm

The western corn rootworm (WCR), Diabrotica virgifera virgifera LeConte, is a destructive pest of maize, Zea mays L. in North America and Europe. Larvae and pupae can be controlled with entomopathogenic nematodes (EPN) of the genus Heterorhabditis. When maize is attacked by WCR, the roots of some maize varieties emit (E)-beta-caryophyllene that attract EPN to the pest larvae. To use synthetic (E)-beta-caryophyllene in bioassays for the genetic selection of EPN strains with enhanced chemotactic response to a volatile emitted from the damaged root when attacked by larvae of the WCR, different laboratory bioassays were tested. Three sand assays and one agar assay used synthetic (E)-beta-caryophyllene as an attractant for H. megidis. In none of the assays, attraction of the nematodes to (E)-beta-caryophyllene was recorded. Possible reasons why (E)-beta-caryophyllene was not attracting EPN in the bioassays are discussed.