Machial Laura A, Lindgren B Staffan, Steenweg Robin W, Aukema Brian H
University of Northern British Columbia, Prince George, British Columbia, Canada.
Environ Entomol. 2012 Jun;41(3):578-86. doi: 10.1603/EN11169.
Warren root collar weevil, Hylobius warreni Wood, is a native, flightless insect distributed throughout the boreal forest of North America. It is an emerging problem in young plantings of lodgepole pine, Pinus contorta variety latifolia, in western Canada, where larval feeding can kill young trees by girdling the root collar. Susceptible plantings are becoming more abundant following salvage harvesting and replanting activities in the wake of an ongoing epidemic of mountain pine beetle, Dendroctonus ponderosae (Hopkins). Previous studies using mark-trap-recapture methods found that movement rates of adult H. warreni were elevated in areas with high numbers of dead trees, consistent with a hypothesis that the insects immigrate from stands with high mountain pine beetle-caused tree mortality to young plantings in search of live hosts. Sampling methods were necessarily biased to insects captured in traps; however, potentially missing individuals that had died, left the study area, or simply remained stationary. Here, we used harmonic radar to examine weevil movement in three different habitats: open field, forest edge, and within a forest. We were able to reliably monitor all but two of 36 insects initially released, over 96 h (4 d). Weevils released in the open field had the highest rates of movement, followed by weevils released at the forest edge, then weevils released within the forest. Movement declined with decreasing ambient air temperature. Our results suggest that weevils tend to be relatively stationary in areas of live hosts, and hence may concentrate in a suitable area once such habitat is found.
沃伦根颈象甲（Hylobius warreni Wood）是一种原产于北美的不会飞的昆虫，分布于北美北方森林。在加拿大西部，它已成为扭叶松（Pinus contorta variety latifolia）幼龄种植林的一个新问题，其幼虫取食会通过环割根颈导致幼树死亡。在山松甲虫（Dendroctonus ponderosae (Hopkins)）持续流行后进行的抢救性采伐和重新造林活动，使得易受侵害的种植林越来越多。以前使用标记 - 诱捕 - 再捕获方法的研究发现，在死树数量多的地区，成年沃伦根颈象甲的移动速率会升高，这与一种假设相符，即这些昆虫会从山松甲虫导致树木死亡率高的林分迁移到幼龄种植林寻找活的寄主。采样方法必然会偏向于捕获在陷阱中的昆虫；然而，可能会遗漏已经死亡、离开研究区域或只是保持静止的个体。在这里，我们使用谐波雷达来研究象甲在三种不同栖息地的移动情况：开阔地、森林边缘和森林内部。在96小时（4天）内，我们能够可靠地监测最初释放的36只昆虫中的34只。在开阔地释放的象甲移动速率最高，其次是在森林边缘释放的象甲，然后是在森林内部释放的象甲。移动速率随着环境气温的降低而下降。我们的结果表明，象甲在有活寄主的区域往往相对静止，因此一旦找到合适的栖息地，它们可能会集中在该区域。
