水稻因雜草競爭，導致產量的降低，在移植稻田約為25.0%，直播稻田則高達71.2%。水田雜草之防除，傳統方式全賴人工除草，但自民國60年代初期，農業工資受急速工商業發展之刺激而形上漲，稻農仍逐漸採用殺草劑除草，以代替人工除草方法，目前以化學除草的水田面積，就臺中地區而言，佔本區水田總面積的95.34%，所用的殺草劑以Butachlor為主，佔殺草劑施用面積之66.15%，Benthiocarb為12.53%及Chloromethoxynil為16.65%，居次要地位。由於長期施用類似的殺草劑，本區水田雜草相已發生改變，往日所常用之殺草劑，必須行某種程度的調整，方能有效的控制田間的雜草。目前化學除草法所面臨之問題有：基本應用研究不足，有待加強。殺草劑名稱繁雜，有待統一。及農民智識不夠，有待教育。

Weeds in the paddy fields had been traditionally controlled by hands in Taiwan. Since late 1960, large increase in cost of labor and the diminishing supply of farm labor. chemical weeding methods have become popular. In central Taiwan, weed control by chemicals was increased from 19% in 1972 to more than 95 % of the total ri ce producing area in 1980. At present time, the most popular herbicides are butachlor, benthiocarb and chloromethoxynil which are counted to 66%, 13%, and 17% of the total chemical weeding area, respectively. The estimated yield losses of rice grain are 25% for transplanted rice and 71 % for direct seeded rice caused by weed competition. However, this yield losses vary with weed species, density and time of control, etc. To strength the basic research. to simplify the name of herbicides and to screen the more effective chemicals are the major tasks of the development in chemical weed control in Taiwan .