Italian ryegrass is one of the most troublesome weeds worldwide because of the rapid evolution of herbicide resistance in this species. Oregon tall fescue seed production requires high seed purity, demanding good control of Italian ryegrass. The necessity to control herbicide-resistant Italian ryegrass and maintain tall fescue seed purity created interest in new chemical management options. The objectives of this study were to assess the effects of synthetic auxin herbicides on seed viability of Italian ryegrass biotypes and the feasibility of this management strategy for use in tall fescue seed production. Eight treatments of synthetic auxin herbicides were applied to Italian ryegrass and tall fescue at two growth stages (boot and anthesis): dicamba (1.0 and 2.2 kg ae ha−1), 2,4-D (1.1 and 2.2 kg ae ha−1), aminopyralid (0.5 kg ae ha−1), dicamba + 2.4-D (0.8 + 1.1 kg ae ha−1), 2.4-D + clopyralid (1.1 + 0.3 kg ae ha−1), and halauxifen-methyl + florasulam (0.4 kg ae ha−1 + 0.4 kg ai ha−1). Aminopyralid applied at boot and anthesis stages of Italian ryegrass reduced seed viability. Aminopyralid treatments reduced seed viability and weight of Italian ryegrass more than 50% compared to the control. Four biotypes from different locations in western Oregon with different types of herbicide resistance were sprayed, and differences in aminopyralid effect among Italian ryegrass biotypes were documented. Aminopyralid reduced the speed of germination by 1 to 2 d. Aminopyralid treatments had a greater effect when applied at the anthesis stage and had a greater negative impact on tall fescue. Tall fescue plants were more susceptible to aminopyralid, so this management practice is not feasible for tall fescue seed production. Future studies are needed to understand the physiological mechanisms involved in the reduced seed viability and to define an optimum aminopyralid rate for different Italian ryegrass biotypes.

中文翻译：

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合成生长素除草剂在高羊茅种子生产中抑制意大利黑麦草（Lolium perenne ssp. multiflorum）种子活力的应用

意大利黑麦草是世界上最麻烦的杂草之一，因为该物种的除草剂抗性迅速发展。俄勒冈高羊茅种子生产要求种子纯度高，需要对意大利黑麦草进行良好控制。控制抗除草剂的意大利黑麦草和保持高羊茅种子纯度的必要性引起了人们对新的化学管理选择的兴趣。本研究的目的是评估合成生长素除草剂对意大利黑麦草生​​物型种子活力的影响，以及该管理策略用于高羊茅种子生产的可行性。八种合成生长素除草剂处理用于意大利黑麦草和高羊茅在两个生长阶段（启动期和开花期）：麦草畏（1.0 和 2.2 kg ae ha-1), 2,4-D (1.1 和 2.2 kg ae ha-1), 氨基吡啶 (0.5 kg ae ha-1)、麦草畏 + 2.4-D (0.8 + 1.1 kg ae ha-1), 2.4-D + clopyralid (1.1 + 0.3 kg ae ha-1) 和 halauxifen-methyl + 氟磺草胺 (0.4 kg ae ha-1+ 0.4 公斤艾哈-1）。在意大利黑麦草的孕穗期和开花期施用氨基吡啶降低了种子活力。与对照相比，氨基吡啶处理使意大利黑麦草的种子活力和重量降低了 50% 以上。喷洒了来自俄勒冈州西部不同地点、具有不同类型除草剂抗性的四种生物型，并记录了意大利黑麦草生​​物型间氨基吡咯作用的差异。氨基吡啶使发芽速度降低 1～2 d。氨基吡啶处理在开花期应用时效果更大，对高羊茅产生更大的负面影响。高羊茅植物更容易感染氨基吡啶，因此这种管理做法对于高羊茅种子生产是不可行的。