Insect pests pose a global threat to crop yield. Biological control by natural enemies aims to reduce pest damage in a sustainable way. Cereal leaf beetles (CLB; spp.) are major pests in small-grain cereals. We studied the effect of natural enemies on CLB damage and its consequences on yield within its native distribution area in Europe. In exclusion cage experiments and by documenting a naturally occurring CLB damage gradient, we found that CLB damage reduced yield, but natural enemy action reduced the damage by CLB. Comparing exclusion and open treatments on artificially CLB-infested plants, plants accessible to natural enemies had 30% less leaf damage. CLB damage significantly affected yield parameters. Thousand grain weight was 22–29% less in maximum leaf damage scenarios. In the damage gradient field, maximal infestation reduced grain yield by 52%. However, maximal damage occurred only on a few plants and over small areas. In natural infestation cases, the number of CLB larvae per plant had a median of zero; nevertheless, there were more than 35 larvae on 10% of the plants. Patchiness explained 40% of CLB damage variance. Damage was unevenly distributed; as a result, thousand grain weight decreased only by 1.6% for 75% of the plants but by 18% for 10% of the plants. In the natural damage gradient, the estimated yield loss for the entire field was 16% due to CLB. Skewed CLB distribution may lead to perceptible yield losses locally, but natural enemies may limit overall damage to the crop.

中文翻译：

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谷物叶甲虫（Oulema spp.）的损害会降低产量，并且当天敌行动被阻止时，损害会更加严重


害虫对农作物产量构成全球威胁。天敌生物防治旨在以可持续的方式减少害虫损害。谷物叶甲虫（CLB；spp.）是小粒谷物的主要害虫。我们研究了天敌对 CLB 损害的影响及其对欧洲原生分布区产量的影响。在排除笼实验中并通过记录自然发生的 CLB 损害梯度，我们发现 CLB 损害降低了产量，但天敌的行动减少了 CLB 造成的损害。与对人工 CLB 侵染植物的排斥和开放处理相比，天敌可接近的植物的叶子损伤减少了 30%。 CLB 损伤显着影响产量参数。在最大叶片损伤情况下，千粒重减少 22-29%。在损害梯度场中，最大虫害使粮食产量减少 52%。然而，最大的损害只发生在少数植物和小面积上。在自然侵染情况下，每株植物的 CLB 幼虫数量中位数为零；然而，10%的植物上有超过35只幼虫。补丁性解释了 40% 的 CLB 伤害差异。损害分布不均匀；结果，75%的植物千粒重仅下降了1.6%，但10%的植物千粒重下降了18%。在自然损害梯度中，由于 CLB，整个田地的产量估计损失为 16%。 CLB 分布的倾斜可能会导致局部明显的产量损失，但天敌可能会限制对作物的总体损害。