Department of Entomology, University of Georgia, 1109 Experiment St., Griffin, GA 30223-1797, USA.
J Econ Entomol. 2011 Feb;104(1):288-98. doi: 10.1603/ec10163.
Understanding how fertilization affects host resistance to hemlock woolly adelgid, Adelges tsugae Annand (Hemiptera: Adelgidae), is important because fertilizers are often used to grow resistant selections to a suitable size for testing. We evaluated four hemlock species (Tsuga) under three different fertilizer regimes to assess whether fertility affected resistance to the adelgid and to determine whether it affected feeding preferences of the adelgid predators Laricobius nigrinus Fender and Sasajiscymnus tsugae (Sasaji & McClure). Treatments were long-term fertilization (from June 2008 to June 2009), short-term fertilization (from March to June 2009), and no fertilizer. Fertilizer was applied biweekly with 240 ppm N by using water-soluble fertilizer (N-P-K, 20:20:20). Plants (>1 yr old) were artificially infested with adelgids on 31 March 2009. Among unfertilized hemlocks (n=10 per species), foliar N was highest in Tsuga mertensiana (Bong.) CarriBre and lowest in T. chinensis (Franch.) E. Pritz. Significantly more progredien ovisacs or sisten eggs were present on T. mertensiana than on the other hemlock species with none on unfertilized T. chinensis. A. tsugae adults on T. heterophylla (Raf.) Sarg. were unaffected by fertility, but densities of developing A. tsugae nymphs were higher on unfertilized T. heterophylla plants than on fertilized T. heterophylla plants regardless of fertilizer treatment. Both L. nigrinus and S. tsugae consumed more adelgid eggs that developed on fertilized T. canadensis than from unfertilized plants. The predators did not exhibit this preference for adelgid eggs from females that developed on T. heterophylla or T. mertensiana.
了解受精如何影响寄主对铁杉羊毛衣鱼（Adelges tsugae Annand）的抗性很重要，因为肥料通常用于培育抗性选择，以达到适合测试的大小。我们评估了三种不同肥料制度下的四个铁杉物种（Tsuga），以评估肥力是否影响对衣鱼的抗性，并确定它是否影响衣鱼捕食者黑缘步甲（Laricobius nigrinus Fender）和 Sasajiscymnus tsugae（Sasaji & McClure）的取食偏好。处理方法为长期施肥（2008 年 6 月至 2009 年 6 月）、短期施肥（2009 年 3 月至 6 月）和不施肥。每两周用 240ppm N 的水溶性肥料（N-P-K，20:20:20）进行施肥。2009 年 3 月 31 日，人工对植物（>1 年生）进行衣鱼侵染。在未施肥的铁杉中（每种植物 10 株），Tsuga mertensiana（Bong.）CarriBre 的叶片氮含量最高，而 T. chinensis（Franch.）E. Pritz. 的叶片氮含量最低。与其他铁杉种相比，Tsuga mertensiana 上的 progredien ovisacs 或 sisten eggs 明显更多，而在未施肥的 T. chinensis 上则没有。A. tsugae 成虫在 T. heterophylla（Raf.）Sarg. 上不受肥力影响，但在未施肥的 T. heterophylla 植株上，发育中的 A. tsugae 若虫密度高于施肥的 T. heterophylla 植株，而与肥料处理无关。L. nigrinus 和 S. tsugae 对来自施肥的 T. canadensis 的衣鱼卵的取食量大于来自未施肥植物的衣鱼卵。捕食者对在 T. heterophylla 或 T. mertensiana 上发育的雌虫产生的衣鱼卵没有这种偏好。
