α-Copaene is an attractant, synergistic with quercivorol, for improved detection of Euwallacea nr. fornicatus (Coleoptera: Curculionidae: Scolytinae)

Abstract

The tea shot-hole borer, Euwallacea fornicatus Eichhoff, is an ambrosia beetle endemic to Asia and a pest of commercial tea, Camellia sinensis (L.) Kuntze. Recently, a complex of species morphologically similar to E. fornicatus has been recognized, which includes new pests established in Israel and the USA, both in California and Florida. Collectively termed E. nr. fornicatus, these cryptic species carry symbiotic Fusarium spp. fungi, some of which cause dieback disease in susceptible hosts, which include avocado, Persea americana Miller. Due to the threat to this economically important crop, research was initiated to evaluate efficacy of kairomone-based lures for detection of the beetle in Florida (termed the Florida tea shot hole borer, FL-TSHB). A series of field tests were conducted in 2016 in commercial avocado groves known to have FL-TSHB at various population levels. All tests evaluated lures containing quercivorol (p-menth-2-en-1-ol) and α-copaene, presented separately and in combination; and one test evaluated effect of trap type on beetle captures. In addition, electroantennography (EAG) was used to quantify female olfactory responses to lure emissions. This study identified (-)-α-copaene as a new attractant for FL-TSHB, equivalent in efficacy to quercivorol (the standard lure for Euwallacea detection in the USA); however, the combination of lures captured significantly more FL-TSHB than either lure alone. This combination resulted in synergistic attraction at two field sites and additive attraction at a third site. Sticky panel traps captured more FL-TSHB than comparably-baited Lindgren funnel traps. Females engaged in host-seeking flight from 11:00 to 16:00 hr (EST), with peak numbers observed between 12:00 and 13:00 hr. EAG analyses confirmed olfactory chemoreception of both kairomones, with a higher response elicited with the combination of volatiles. Results indicate that detection of pest E. nr. fornicatus in Florida can be improved by using a two-component lure consisting of p-menth-2-en-1-ol and (-)-α-copaene.

Dispersal behaviour of Euwallacea nr. fornicatus (Coleoptera: Curculionidae: Scolytinae) in avocado groves and estimation of lure sampling range

“…Field Test 2 also confirms previous reports that the combination of quercivorol and α‐copaene lures is more effective than either lure alone (Kendra et al ., ; Owens et al ., 2018b). The combination treatment recaptured 2.8‐fold more beetles than single lures, although all lure treatments resulted in similar recapture proportions as a function of distance from the release point.…”

“…nr. fornicatus (Kendra et al ., ). Traps were hung from branches in shaded locations between 1.75 and 2.5 m above the ground.…”

“…Coated beetles were then transferred to a clean plastic container lined with tissue for transport to field sites. Each release used a minimum of 150 marked beetles and releases were initiated before 10.30 h, prior to the beetle's flight window observed in south Florida (Kendra et al ., ). The container was taken to a central release point in the grove, placed on a plastic sheet on the ground underneath and adjacent to the trunk of an avocado tree, and the lid was gently removed to allow passive escape of the beetles.…”

“…fornicatus (Kendra et al ., ). Further evaluations demonstrated that α‐copaene is equal in attraction to quercivorol and that a combination of semiochemicals results in additive to synergistic increases in trap capture (Kendra et al ., ). This two‐component lure is the most effective attractant identified to date for E .…”

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“…Avocado is now threatened in California and Florida, and more than one quarter of all street trees in southern California are reproductive hosts susceptible to attack (Lesser 1996;Eskalen and Stouthamer 2012;Mendel et al 2012;Freeman et al 2013b;Eskalen et al 2013;Carrillo et al 2016;Cooperband et al 2016;Kendra et al 2017;Stouthamer et al 2017).…”