Department of Entomology, University of Georgia, 122 S. Entomology Dr., Tifton, GA 31794, USA.
J Econ Entomol. 2011 Dec;104(6):1918-27. doi: 10.1603/ec11022.
We studied the distribution of hemlock woolly adelgid, Adelges tsugae Annand (Hemiptera: Adelgidae), within hemlock trees for three summer (progrediens) and two winter (sistens) generations in northern Georgia. Eastern hemlock, Tsuga canadensis (L.) Carrière, trees were treated with 0, 10, or 25% of 1.5 g of imidacloprid per 2.5 cm of tree diameter at breast height and fertilized or not in a factorial design. Adelgid ovisacs per centimeter of branch were more abundant from June 2007 to June 2008 in the upper tree crown of insecticide untreated trees and when all trees were combined and that was the general trend for most comparisons. However, ovisacs were more abundant in the lower crown of insecticide treated trees in June 2008. More sistens nymphs settled on the upper crown branches than on the lower branches in summers 2007 and 2008. Higher eggs per ovisac were observed in the upper crown in February 2008 and in both the winter and summer 2009. In contrast, adelgids were more fecund in the lower crown in June 2008. On fertilized trees, eggs laid per adult were higher in the upper crown in February 2008. In summer 2008, eggs per ovisac were higher in the lower crown, but this reversed again to the upper crown by summer 2009. New growth of branches also varied among sample dates. These data demonstrate the variable distribution of adelgid and hemlock growth within trees over time and suggest that sampling only one crown area will not provide accurate estimates of adelgid densities.
我们研究了在佐治亚州北部的三个夏季（progrediens）和两个冬季（sistens）世代中，铁杉羊毛衣鱼 Adelges tsugae Annand（半翅目：衣鱼科）在铁杉树内的分布。在一个因子设计中，用 0、10 或 25%的 1.5 克每 2.5 厘米胸高处树直径的吡虫啉处理东方铁杉 Tsuga canadensis（L.）Carrière 树，并施肥或不施肥。2007 年 6 月至 2008 年 6 月，在未处理杀虫剂的树木的树冠上部，以及当所有树木合并时，每厘米树枝上的衣鱼卵囊数量更多，这是大多数比较的总体趋势。然而，在 2008 年 6 月，处理过杀虫剂的树木的树冠下部的卵囊数量更多。2007 年和 2008 年夏季，更多的 sistens 若虫降落在树冠上部的树枝上，而不是下部的树枝上。2008 年 2 月和 2009 年冬夏两季，在上部树冠中观察到每卵囊的卵数量更高。相比之下，在 2008 年 6 月，下部树冠的衣鱼繁殖力更强。在施肥的树上，2008 年 2 月，在上部树冠中每只成虫产卵的数量更高。2008 年夏季，每卵囊的卵数量在上部树冠中更高，但到 2009 年夏季又恢复到上部树冠。树枝的新生长也在不同的采样日期之间有所变化。这些数据表明，随着时间的推移，衣鱼和铁杉的生长在树木内的分布是可变的，这表明仅对一个树冠区域进行采样，不会提供衣鱼密度的准确估计。
