<I>Xyleborus glabratus</I>, <I>X. affinis</I>, and <I>X. ferrugineus</I> (Coleoptera: Curculionidae: Scolytinae): Electroantennogram Responses to Host-Based Attractants and Temporal Patterns in Host-Seeking Flight

Abstract

The redbay ambrosia beetle, Xyleborus glabratus Eichhoff, is an exotic wood-boring insect that vectors the mycopathogen responsible for laurel wilt, a lethal vascular disease of trees in the Lauraceae, including avocado (Persea americana Mill.). Effective semiochemical-based detection and control programs for X. glabratus will require an understanding of the chemical ecology and host-seeking behaviors of this new invasive pest. This study 1) presents an electroantennography (EAG) method developed for assessment of olfactory responses in ambrosia beetles; 2) uses that new method to quantify EAG responses of X. glabratus, X. affinis, and X. ferrugineus to volatiles from three host-based attractants: manuka oil (essential oil extract from Leptospermum scoparium Forst. & Forst.), phoebe oil (extract from Phoebe porosa Mex.), and wood from silkbay (Persea humilis Nash); and 3) documents temporal differences in host-seeking flight of the sympatric Xyleborus species. Field observations revealed that X. glabratus engages in flight several hours earlier than X. affinis and X. ferrugineus, providing a window for selective capture of the target pest species. In EAG analyses with X. glabratus, antennal response to phoebe oil was equivalent to response to host Persea wood, but EAG response elicited with manuka oil was significantly less. In comparative studies, EAG response of X. glabratus was significantly higher than response of either X. affinis or X. ferrugineus to all three host-based substrates. Future research will use this EAG method to measure olfactory responses to synthetic terpenoids, facilitating identification of the specific kairomones used by X. glabratus for host location.

Analysis of Sesquiterpene Distributions in the Leaves, Branches, and Trunks of Avocado (&lt;i&gt;Persea americana&lt;/i&gt; Mill.)

“…Insight into potential RAB attractants may be gained from comparative studies of known RAB host plants, including analysis of sesquiterpene content and evaluation of relative attractiveness in field tests or laboratory bioassays. However, identification of specific RAB kairomones may be greatly facilitated by combining the chemical sampling methods outlined in this report with a newly developed electroantennography method used to directly quantify the olfactory response from antennae of RAB [35].…”

Attraction of Redbay Ambrosia Beetle, Xyleborus Glabratus, To Leaf Volatiles of its Host Plants in North America

“…Beetles were introduced into the olfactometer between 16:00 and 17:00 hr, and the number of beetles that entered the arms and fell into each trap was counted 16 hr later. This bioassay was performed overnight given that peak activity for X. glabratus is between 17:00 and 19:00 hr Kendra et al 2012). Beetles that did not leave the olfactometer arena were designated as non-responders (NR).…”

“…Additionally, X. glabratus is not attracted to ethanol (Hanula and Sullivan 2008;Johnson et al 2014), a semiochemical indicative of tree stress and decay (Kelsey et al 2014;Kimmerer and Kozlowski 1982) that is used as an attractant for monitoring of various ambrosia beetles and wood borers of the Xyleborini tribe (Miller and Rabaglia 2009;Montgomery and Wargo 1983;Ranger et al 2010). Extensive research has shown that X. glabratus is attracted to the sequiterpenes found within the cambium of their lauraceous hosts (Niogret et al 2011); primarily α-copaene, but also to α-cubebene, α-humulene, and calamenene (Hanula and Sullivan 2008;Kendra et al 2012Kendra et al , 2014aNiogret et al 2011). This led to the widespread use of manuka oil, an essential oil containing high concentration of α-copaene as well as cubeb oil as the primary attractants for trapping and surveying X. glabratus for quarantine and management purposes (Hughes et al 2015;Johnson et al 2014).…”

Laurel Wilt in Natural and Agricultural Ecosystems: Understanding the Drivers and Scales of Complex Pathosystems

“…With X. glabratus, females engage in host-seeking flight during the late afternoon and early evening, several hours earlier than other species of Xyleborus in Florida [90]. While in flight, females orient initially toward long-range olfactory cues; α-copaene appears to be the primary kairomone, but other terpenoids likely contribute to generate an attractive "signature bouquet" of the Lauraceae [66,82,87].…”