Comparative analysis of terpenoid emissions from Florida host trees of the redbay ambrosia beetle, xyleborus glabratus (Coleoptera: Curculionidae: Scolytinae)

Abstract

The redbay ambrosia beetle, Xyleborus glabratus Eichhoff (Coleoptera: Curculionidae: Scolytinae), is an exotic wood-boring insect that vectors Raffaelea lauricola, the fungal pathogen responsible for laurel wilt, a lethal disease of trees in the Lauraceae. First detected in the U.S. near Savannah, GA in 2002, X. glabratus has since spread throughout the southeastern coastal plain causing high mortality in native Persea species, particularly redbay (P. borbonia) and swampbay (P. palustris). Currently, breeding populations of X. glabratus pose an imminent threat to the avocado (P. americana) industry in south Florida. There is a critical need for effective attractants to detect, monitor, and control the spread of this invasive pest. In an effort to identify host-based attractants for dispersing female X. glabratus, we conducted a comparative study of the volatile chemicals emitted from wood of six species of Lauraceae found in Florida: avocado (Persea americana), redbay (P. borbonia), swampbay (P. palustris), silkbay (P. humilis), camphor tree (Cinnamomum camphora), and lancewood (Ocotea coriacea). We compared chemical profiles to those obtained from wood of lychee, Litchi chinensis (Sapindaceae), a presumed non-host found to be highly attractive to X. glabratus in field tests. GC-MS analysis identified 11 terpenoid compounds common to all lauraceous species. Of these, 4 sesquiterpenes were also found in lychee: a-copaene, b-caryophyllene, a-humulene and cadinene. Future research will include field tests and laboratory bioassays to evaluate the roles of each of these potential kairomones.