The Redbay Ambrosia Beetle (Coleoptera: Curculionidae: Scolytinae) Uses Stem Silhouette Diameter as a Visual Host-Finding Cue

Abstract

The redbay ambrosia beetle (Xyleborus glabratus Eichhoff) is an invasive pest and vector of the pathogen that causes laurel wilt disease in Lauraceous tree species in the eastern United States. This insect uses olfactory cues during host finding, but use of visual cues by X. glabratus has not been previously investigated and may help explain diameter-related patterns in host tree mortality. The objective of this study was to determine whether X. glabratus females visually detect silhouettes of tree stems during host finding and are more likely to land on large diameter stems than smaller ones. Three field experiments were conducted in which stem silhouettes (black cylinders or standing nonhost pines) of varying diameters and identical capture surface areas were baited with essential oil lures. The Log10-transformed number of X. glabratus trapped per week increased as a function of silhouette diameter in 2011 and 2012, using artificial silhouette diameters ranging 2-18 and 3-41 cm, respectively. When lures and capture surfaces were attached to standing pines ranging 4-37 cm in diameter, a positive relationship between Log10(X. glabratus trap catch) and stem diameter was modeled using nonlinear quadratic plateau regression and indicated a diameter above which visual attraction was not enhanced; however, there was not a maximum diameter for enhanced X. glabratus attraction that was generally consistent across all experiments. These results 1) indicate that X. glabratus incorporates visual information during host finding, 2) help explain diameter-related patterns of redbay (Persea borbonia (L.) Sprengel) mortality observed during laurel wilt epidemics, and 3) are applicable to the management of this forest pest.

Ecological implications of Laurel Wilt infestation on Everglades Tree Islands, southern Florida

“…It is uncertain whether smaller individuals or resprouts will remain. Mayfield and Brownie (2013) have shown experimentally that the redbay ambrosia beetle visually cues on large-diameter stems, and that may partially explain the greater survival rates of smaller individuals seen in some studies. The basal sprouting of swamp bays possibly will allow existing genets to survive for an extended period, much like the American chestnut continues to survive as small resprouts several decades after all mature trees were killed (Freinkel, 2007).…”

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

“…Leaf volatiles potentially could be used by X. glabratus as a long-range cue, or a cue indicating the presence of redbay in the foraging area. Following this long-range attraction through leaf volatiles, tree selection might be mediated through visual rather than olfactory cues, as X. glabratus are known to be attracted by artificial stems of larger diameter (Mayfield and Brownie 2013). Additionally, bark requires damage for volatile release, and once on the tree, the beetles will subsequently determine if the host is suitable for colonization and reproduction, guiding the decision to bore into the wood (Kendra et al 2014a;Kuhns et al 2014a).…”

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

“…A recent study demonstrated experimentally that females indeed utilize stem diameter as a host-seeking cue [41], but this visual signal only synergizes attraction when in the proper chemical context. Thus, X. glabratus does not bore into trunks/branches of suitable diameter if they lack the appropriate chemical cues (e.g.…”

“…Test 1 was conducted at the Royce Ranch Unit (N 27°38′410″, W 81°34′307″) from 24 September to 12 November 2010 (7-wk test), and evaluated attraction to five species of Lauraceae: redbay, swampbay, silkbay, avocado, and lancewood. In addition, the test included two controls, consisting of an unbaited trap (to assess random background captures) and a trap baited with live oak (a non-host bolt treatment, to assess potential captures resulting from visual cues [41]). Test 2 was conducted at the Highlands Park Estates (N 27°21′032″, W 81°19′837″) from 4 August to 15 September 2011 (6-wk test), and compared captures of X. glabratus with bolts of camphor tree, sassafras, northern spicebush, California bay laurel, silkbay (an internal control for comparison with results from test 1), and an unbaited trap.…”