Weedy rice (WR) (Oryza spp.) is the most troublesome weed infesting rice paddies in Brazil. Several changes have occurred in this region regarding crop management, especially WR control based on the Clearfield® (CL) rice production system launched in 2003. This survey’s objective was to evaluate the WR infestation status by assessing the producers’ perception and the management practices used in southern Brazil after 18 yr of CL use in Brazil. Rice consultants and extension agents distributed a questionnaire to 213 producers in the Rio Grande do Sul (RS) and Santa Catarina (SC) states in the 2018 to 2019 growing season. In RS, most farms are larger than 150 ha, and farmers have adopted the CL system for more than 2 yr and use minimal or conventional tillage, permanent flooding, clomazone PRE tank-mixed with glyphosate at the rice spiking stage, and crop rotation with soybean [Glycine max (L.) Merr.] or pasture. In SC, rice farms are small, averaging from 20 to 30 ha, farmers predominantly plant pre-germinated rice and do not rotate rice with other crops, and roguing is practiced. Comparing both states, the CL system is used in 99.5% and 69.3% of the total surveyed rice areas in RS and SC, respectively. Imidazolinone-resistant WR is present in 68.4% and 26.6% of rice farms in RS and SC, respectively. Rice cultivation in Brazil is currently coexisting with WR with minimal integration of control methods. However, integrated practices can control this weed and are fundamental to the sustainability of systems based on herbicide-resistant rice cultivars.

中文翻译：

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巴西南部杂草稻（Oryza spp.）的侵扰状况和管理措施

杂草稻 (WR) (稻米spp.) 是巴西稻田最棘手的杂草。该地区在作物管理方面发生了一些变化，尤其是基于 Clearfield 的 WR 控制®(CL) 水稻生产系统于 2003 年启动。本次调查的目的是通过评估巴西南部使用 CL 18 年后生产者的看法和管理实践来评估 WR 侵染状况。水稻顾问和推广代理在 2018 年至 2019 年的生长季节向南里奥格兰德州 (RS) 和圣卡塔琳娜州 (SC) 的 213 名生产者分发了一份调查问卷。在 RS，大多数农场的面积超过 150 公顷，农民采用 CL 系统超过 2 年，并使用最少或常规耕作、永久淹水、在稻穗期与草甘膦罐混的异恶草酮 PRE 以及与大豆 [最大甘氨酸(L.) Merr.] 或牧场。在南卡罗来纳州，稻田很小，平均为 20 至 30 公顷，农民主要种植预发芽的稻米，不与其他作物轮作水稻，并实行轮作。比较这两个州，CL 系统分别用于 RS 和 SC 总调查水稻面积的 99.5% 和 69.3%。RS和SC分别有68.4%和26.6%的稻田存在咪唑啉酮抗性WR。巴西的水稻种植目前与 WR 共存，控制方法的整合最少。然而，综合实践可以控制这种杂草，并且对于基于抗除草剂水稻品种的系统的可持续性至关重要。