Department of Entomology, 219 Hodson Hall, 1980 Folwell Ave., University of Minnesota, St. Paul, MN 55108, USA.
J Econ Entomol. 2010 Aug;103(4):1483-92. doi: 10.1603/ec10012.
The soybean aphid, Aphis glycines Matsumura (Hemiptera: Aphididae), is currently the most important insect threat to soybean, Clycine max (L.) Merr., production in the North Central United States. Field cage studies are a key tool in investigating the potential of natural enemies and host plant resistance to control this pest. However, a major constraint in the use of cage studies is the limited number of treatments and replicates that can be used as aphid densities frequently become so large as to limit the number of experimental units that can be quantified. One way to overcome this limitation is to develop methods that estimate whole-plant aphid densities based on a reduced sampling plan. Here, we extend an existing method, node-sampling, used for estimating aphid populations in open field conditions and apply it to caged populations. We show that parameters calculated under open field conditions are inappropriate to estimate caged populations. In contrast, using four independent data sets of caged populations and a cross-validation technique, we demonstrate that a three-node sampling unit and a weighted formula provide accurate and robust estimates of whole-plant aphid density. This method reduced the number of aphids counted per plant by and average of 60%, with greater reductions at higher aphid densities. We further demonstrate that nearly identical statistical results were obtained when whole-plant or node-sampling estimates were used in the analysis of two case studies. The reduced sample unit method developed here saves time without sacrificing efficiency so that more plants, replications, or studies can be conducted that will lead to improved soybean aphid management.
大豆蚜，Aphis glycines Matsumura（半翅目：蚜科），是目前北美中部地区大豆生产中最重要的昆虫威胁。田间笼养研究是调查天敌和寄主植物抗性控制这种害虫潜力的关键工具。然而，笼养研究的一个主要限制是可以使用的处理和重复次数有限，因为蚜虫密度经常变得非常大，以至于限制了可以量化的实验单位数量。克服这一限制的一种方法是开发基于减少采样计划估算整株蚜虫密度的方法。在这里，我们扩展了一种现有的方法，即节点采样，用于估算开放条件下的蚜虫种群，并将其应用于笼养种群。我们表明，在开放条件下计算的参数不适合估计笼养种群。相比之下，我们使用四个独立的笼养种群数据集和交叉验证技术，证明了三个节点采样单元和加权公式可以提供准确和稳健的整株蚜虫密度估计值。这种方法使每株计数的蚜虫数量平均减少了 60%，在更高的蚜虫密度下减少得更多。我们进一步证明，当使用整株或节点采样估计值分析两个案例研究时，几乎可以获得相同的统计结果。这里开发的减少样本单元方法节省了时间而不影响效率，因此可以进行更多的植物、重复或研究，从而改善大豆蚜的管理。
