Mayfield Albert E, Brownie Cavell
USDA Forest Service, Southern Research Station, Asheville, NC 28804, USA.
Environ Entomol. 2013 Aug;42(4):743-50. doi: 10.1603/EN12341.
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.
红脂大小蠹（Xyleborus glabratus Eichhoff）是一种入侵性害虫，也是导致美国东部月桂科树种发生月桂枯萎病的病原体的传播媒介。这种昆虫在寻找寄主时利用嗅觉线索，但此前尚未研究过红脂大小蠹对视觉线索的利用情况，而这可能有助于解释寄主树木死亡率与直径相关的模式。本研究的目的是确定红脂大小蠹雌虫在寻找寄主时是否能通过视觉检测到树干的轮廓，以及是否比小直径树干更有可能降落在大直径树干上。进行了三项田间试验，用精油诱饵诱捕不同直径但捕获表面积相同的树干轮廓（黑色圆柱体或直立的非寄主松树）。在2011年和2012年，使用分别为2 - 18厘米和3 - 41厘米的人工轮廓直径，每周诱捕到的红脂大小蠹数量的对数转换值随轮廓直径的增加而增加。当诱饵和捕获表面附着在直径为4 - 37厘米的直立松树上时，使用非线性二次平台回归对红脂大小蠹诱捕量的对数与树干直径之间的正相关关系进行建模，结果表明存在一个直径，超过该直径视觉吸引力不会增强；然而，在所有实验中，红脂大小蠹吸引力增强的最大直径并不一致。这些结果1）表明红脂大小蠹在寻找寄主时会整合视觉信息，2）有助于解释月桂枯萎病流行期间观察到的红海湾（Persea borbonia (L.) Sprengel）死亡率与直径相关的模式，3）适用于这种森林害虫的管理。
