Weedy rice is a conspecific weed of cultivated rice (Oryza sativa L.) and is a primary weed of direct‐seeded rice production systems worldwide. The shift in the method of establishing rice, that is, from transplanting to direct seeding, is considered the main reason for the emergence of weedy rice in Asia and, more recently, Japan. Japan has increasingly adopted directly seeded rice, even though this practice remains limited. In this study, I confirmed the relationship between weedy red rice emergence and the adoption of direct‐seeded rice in Japan. Twenty‐seven areas from eight prefectures infested with weedy rice were selected to confirm the relationship between the rice planting method and the emergence of weedy rice. Fields that were severely infested with weedy rice were selected as survey fields for this study. I found no relationship between the method of planting rice and weedy rice emergence. Changes to herbicide application, duration of rice production and hand weeding also contribute to the emergence of weedy rice in transplanted rice fields in Japan. The results of this study indicate that weedy rice could become a serious problem in Japan, even in transplanted rice fields.

中文翻译：

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杂草稻对日本的移植稻生产系统构成了新的威胁

杂草稻是一种栽培稻的杂草（Oryza sativaL.），是世界范围内直接播种水稻生产系统的主要杂草。稻作方法的转变，即从移栽到直接播种，被认为是亚洲乃至日本最近出现杂草稻的主要原因。尽管这种做法仍然受到限制，但日本越来越多地采用直接播种稻米。在这项研究中，我证实了杂草红米的出现与日本直接播种稻的采用之间的关系。选择了八个县的27个杂草稻受害地区，以确认水稻种植方法与杂草稻出苗之间的关系。本研究选择了杂草水稻严重侵染的田地作为调查田地。我发现种植稻米的方法与杂草稻出苗之间没有关系。除草剂施用，水稻生产持续时间和人工除草的变化也促使杂草稻在日本的稻田中出现。这项研究的结果表明，即使在稻田里，杂草水稻在日本也可能成为一个严重的问题。