Abstract The cereal leaf beetle, Oulema melanopus L., is an economically important pest species, reducing crop yields in many cereal growing parts of the world. Available studies on yield depression in winter wheat in relation to the density of O. melanopus revealed inconsistent results, creating uncertainty about economic thresholds for pest control. We present results from a series of controlled field trials over a 4-yr period (2014–2017) in Switzerland to examine the impact of artificial defoliation (0, 20, 40, and 60% of flag leaf area removed in 1-m2 field plots) on yield and yield components in winter wheat. The applied defoliation treatments correspond to field infestations levels of approximately 2–6 larvae per stem. Analysis of the combined data from 11 location-years revealed a significant linear decrease in yield per ear with increasing defoliation intensity. Yield per ear declined at a rate of 1.14% (SE = 0.28) per 10 percentage-point increase in defoliation. Similar results were found in a parallel series of field trials in which a 40% defoliation treatment was applied to eight common wheat cultivars. Interestingly, however, three cultivars showed complete tolerance in yield to defoliation. Data from two trials with natural defoliation by larvae revealed equally low levels of yield loss by feeding of O. melanopus. Based on the experimentally derived yield loss function, we calculated economic injury levels for a range of crop values. These will serve as benchmarks in the development of IPM decision-support tools for managing cereal leaf beetles in winter wheat.

中文翻译：

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谷叶甲虫（鞘翅目：菊科）对冬小麦经济危害程度的试验评价

摘要 谷叶甲虫 Oulema melanopus L. 是一种重要的经济害虫，在世界许多谷类种植区降低了作物产量。关于冬小麦产量下降与 O. melanopus 密度相关的现有研究揭示了不一致的结果，造成了关于害虫控制的经济阈值的不确定性。我们展示了在瑞士进行的为期 4 年（2014-2017 年）的一系列受控田间试验的结果，以检查人工落叶的影响（在 1 平方米的田地中去除了 0、20、40 和 60% 的旗叶面积）地块）关于冬小麦的产量和产量构成。应用的落叶处理对应于每茎约 2-6 只幼虫的田间侵染水平。对来自 11 个地点年的综合数据的分析显示，随着落叶强度的增加，每穗产量显着线性下降。落叶每增加 10 个百分点，每穗产量下降 1.14% (SE = 0.28)。在一系列平行的田间试验中发现了类似的结果，其中对八种常见小麦品种进行了 40% 的落叶处理。然而，有趣的是，三个品种对落叶的产量表现出完全的耐受性。来自幼虫自然落叶的两项试验的数据显示，喂食黑夜蛾的产量损失水平同样低。基于实验得出的产量损失函数，我们计算了一系列作物价值的经济损失水平。