Bearded sprangletop is a problematic weed in California rice production and few herbicides provide effective control. As control of bearded sprangletop has declined, grower suspicion of resistance to clomazone has increased, because of the continuous rice cropping system and herbicide dependence in the region. The objectives of this research were to confirm clomazone resistance in bearded sprangletop populations and determine the level of resistance. Seed from 21 suspected clomazone-resistant populations was collected from the California rice growing region. A greenhouse experiment was conducted to determine population sensitivity to clomazone. Clomazone was applied into the water to emerging seedlings. Plant ht and control of bearded sprangletop were recorded weekly for 3 wk, plants were then harvested, and dry weight was measured. Of the populations tested, 17 were susceptible and four (5%) were resistant to clomazone. A dose-response assay was conducted using eight doses ranging from an eighth of the full rate to 12 times the full rate. The three most resistant populations had resistant-to susceptible ratios of 1.25×, 2×, and 5× the labeled rate of clomazone. The use of clomazone in California rice production is beneficial; however, it should be used at the appropriate timing and as part of an herbicide program to prevent further development of clomazone resistance.

中文翻译：

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加利福尼亚水稻中胡须花草 (Leptochloa fusca spp. fasicularis) 对异恶草酮反应的调查

胡须花椒是加利福尼亚水稻生产中的一种有问题的杂草，很少有除草剂能提供有效的控制。随着对胡须花冠的控制下降，由于该地区的水稻连作系统和除草剂的依赖，种植者对异恶草酮耐药性的怀疑有所增加。这项研究的目的是确认有胡须的sprangletop 种群对异恶草酮的抗性并确定抗性水平。从加利福尼亚水稻种植区收集了来自 21 个疑似异恶草酮抗性种群的种子。进行了温室实验以确定种群对异恶草酮的敏感性。将异恶草酮施用于水中出苗。在 3 周内每周记录植物 ht 和有胡须的sprangletop 的对照，然后收获植物，并测量干重。在测试的人群中，17 人易感，4 人（5%）对异恶草酮有抗药性。使用从全速率的八分之一到全速率的 12 倍的八种剂量进行剂量反应测定。三个抗药性最强的群体的抗感比分别为异恶草酮标记率的1.25倍、2倍和5倍。在加州水稻生产中使用异恶草酮是有益的；但是，它应该在适当的时间使用，并作为除草剂计划的一部分，以防止进一步发展异恶草酮抗性。和 5 倍异恶草酮的标记率。在加州水稻生产中使用异恶草酮是有益的；但是，它应该在适当的时间使用，并作为除草剂计划的一部分，以防止进一步发展异恶草酮抗性。和 5 倍异恶草酮的标记率。在加州水稻生产中使用异恶草酮是有益的；但是，它应该在适当的时间使用，并作为除草剂计划的一部分，以防止进一步发展异恶草酮抗性。