Biology and Host Associations of Redbay Ambrosia Beetle (Coleoptera: Curculionidae: Scolytinae), Exotic Vector of Laurel Wilt Killing Redbay Trees in the Southeastern United States

Abstract

The redbay ambrosia beetle, Xyleborus glabratus Eichhoff (Coleoptera: Curculionidae: Scolytinae), and its fungal symbiont, Raffaelea sp., are new introductions to the southeastern United States responsible for the wilt of mature redbay, Persea borbonia (L.) Spreng., trees. In 2006 and 2007, we investigated the seasonal flight activity of X. glabratus, its host associations, and population levels at eight locations in South Carolina and Georgia where infestations ranged from very recent to at least several years old. Adults were active throughout the year with peak activity in early September. Brood development seems to take 50-60 d. Wood infested with beetles and infected with the Raffaelea sp. was similar in attraction to uninfested redbay wood, whereas both were more attractive than a nonhost species. Sassafras, Sassafras albidium (Nutt.) Nees, another species of Lauraceae, was not attractive to X. glabratus and very few beetle entrance holes were found in sassafras wood compared with redbay. Conversely, avocado, Persea americana Mill., was as attractive to X. glabratus as swampbay, P. palustris (Raf.) Sarg., and both were more attractive than the nonhost red maple, Acer rubrum L. However, avocado had relatively few entrance holes in the wood. In 2007, we compared X. glabratus populations in areas where all mature redbay have died to areas where infestations were very active and more recent. Trap catches of X. glabratus and numbers of entrance holes in trap bolts of redbay were correlated with the number of dead trees with leaves attached. Older infestations where mature host trees had been eliminated by the wilt had low numbers of beetles resulting in trap catches ranging from 0.04 to 0.12 beetles per trap per d compared with 4-7 beetles per trap per d in areas with numerous recently dead trees. Our results indicate beetle populations drop dramatically after suitable host material is gone and provide hope that management strategies can be developed to restore redbay trees. The lack of attraction of X. glabratus to sassafras suggests that spread of X. glabratus may slow once it is outside the range of redbay.

North American Lauraceae: Terpenoid Emissions, Relative Attraction and Boring Preferences of Redbay Ambrosia Beetle, Xyleborus glabratus (Coleoptera: Curculionidae: Scolytinae)

“…After departing the natal tree, females (usually sibling mated) orient toward long-range olfactory cues while in flight. It does not appear that X. glabratus utilizes sex or aggregation pheromones, since bolts from trees infested with conspecifics are no more attractive than bolts from uninfested trees [2]. As primary colonizers of healthy trees [1], females are attracted to natural volatiles emitted by host Lauraceae [29], [31], and the current study identified four sesquiterpenes that were correlated with attraction: α-cubebene, α-copaene, α-humulene, and calamenene.…”

“…and P. palustris (Raf.) Sarg., respectively] have been decimated throughout the southeastern United States [1]–[2], and currently avocado ( P. americana Mill.) is threatened in south Florida [3].…”

“…While most xyleborines are broad generalists that target stressed or dying trees (saprotrophic symbiosis) [20], X. glabratus functions ecologically as a primary colonizer, capable of attacking live, apparently-healthy hosts [1]. Consequently, it is not attracted to ethanol [2], [21], a signature volatile of tree decay, which serves as the standard lure for detection of most ambrosia beetles [22]. In addition, X. glabratus is not a host generalist in the United States, but appears to be restricted to the Lauraceae.…”

“…In addition, X. glabratus is not a host generalist in the United States, but appears to be restricted to the Lauraceae. To date, at least 12 U.S. species – all in the Lauraceae – have been reported as either hosts of X. glabratus and/or suscepts of laurel wilt [1]–[2], [23]–[27]. It was thought that this host specificity represented a major behavioral shift that accompanied establishment of the founder population in North America [15], but a recent inspection of host records from the Chinese National Insect Collection suggests that X. glabratus shows a preference for Lauraceae in Asia as well [28].…”

Detection and Differentiation between Laurel Wilt Disease, Phytophthora Disease, and Salinity Damage Using a Hyperspectral Sensing Technique

“…One vector of Lw disease is the redbay ambrosia beetle [3,4,7,8]. The redbay ambrosia beetle, Xyleborus glabratus Eichhoff (Coleoptera, Curculionidae, Scolytinae) is associated with fungal symbionts such as Raffaelea lauricola [9,10], a fungus that kills the tree by blocking water flow to the canopy [11].…”