日本耕地面积共500万公顷,其中一半是水稻。日本的特点是面积小,坡度大,雨量足(年降雨量2,000毫米),水流急,如果没有水田,很可能把土坡冲掉,因此水稻有护坡作用。日本环境污染比较严重,而水田对环境保护有重要意义。 战后30年,日本有段时间依靠农药防治害虫,1971年停用六六六后开始考虑综合防治。日本农药比较便宜,禁用农药不可能。以害虫发生量、为害损失及生命表的研究为基础,拟订出经济阈值和防治指标,目前靠防治指标减少用药数量。实际上两种以上害虫 Japan has a total cultivated area of ​​5 million hectares, half of which is paddy. Japan is characterized by its small size, large slope, enough rainfall (annual rainfall of 2,000 mm) and rapid water flow. Without paddy fields, soil slopes are likely to be washed off so that rice has a role of slope protection. Japan’s environmental pollution is more serious, while paddy fields are of great significance to environmental protection. In the 30 years after the war, Japan relied on pest control for some time and started to consider comprehensive prevention and control after the suspension of 666 in 1971. Japanese pesticides cheaper, banned pesticides impossible. Based on the study on pest occurrence, damage loss and life table, economic thresholds and prevention and control indicators are drawn up. At present, prevention and treatment indicators reduce the quantity of drugs used. In fact two or more pests