Alfalfa (Medicago sativa L.) dominates cropping systems in the Western United States and is first in terms of acreage planted in Arizona. The alfalfa weevil, Hypera postica (Gylenhall) and/or Hypera brunneipennis (Boheman), respectively, is the most destructive pest in terms of yield loss in low desert-grown alfalfa hay. The current economic threshold of 15–20 larvae per sweep, established in California in 1975, is currently not suitable or adopted by growers in the western U.S. low desert. Here, we conducted 4 yr of field trials to re-evaluate this economic threshold. Supporting observations of agricultural growers and professionals in the region, our results indicate that the economic threshold established in 1975 is too high. Specifically, one to three large larvae often cause a significant decrease in yield justifying weevil control based on current hay prices and costs of insecticide application. These results are discussed in the context of sustainable alfalfa production in the western U.S. low desert.

中文翻译：

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重新评估低沙漠灌溉苜蓿中苜蓿象鼻虫（鞘翅目：葫芦科）控制的经济伤害水平

紫花苜蓿（Medicago sativa L.）在美国西部的种植系统中占主导地位，并且在亚利桑那州的种植面积方面排名第一。苜蓿象鼻虫 Hypera postica (Gylenhall) 和/或 Hypera brunneipennis (Boheman) 分别是低沙漠生长的苜蓿干草产量损失方面最具破坏性的害虫。1975 年在加利福尼亚制定的当前每次扫掠 15-20 条幼虫的经济阈值目前不适合或不被美国西部低沙漠的种植者采用。在这里，我们进行了 4 年的实地试验，以重新评估这一经济门槛。支持对该地区农业种植者和专业人士的观察，我们的结果表明 1975 年建立的经济门槛过高。具体来说，根据当前的干草价格和杀虫剂应用成本，一到三个大型幼虫通常会导致产量显着下降，从而证明控制象鼻是合理的。这些结果是在美国西部低沙漠可持续紫花苜蓿生产的背景下讨论的。