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三化螟是鄱阳湖区为害水稻的主要害虫之一,1980年以前,各年度间均有不同程度的发生,轻微的年份损失稻谷10～20％,其中以1959、1964和1974年发生数量多、为害重、损失大。特别是1974年未防治或防治不力的早晚稻,白穗率一般在20～30％,严重的达50～70％。但自1976年以后,螟害逐年下降,特别是1980年以来,各代螟虫发生数量都很少,为害十分轻微,一般枯心率和白穗率都在1％以下,不加防治也不会造成经济上的重大损失。其发生轻微的主要原因何在?又与哪些最主要的栽培耕作制度、综防措施的改变关系更为密切?现试分析如下:
Borer borer is one of the major pests that damage rice in Poyang Lake region. Before 1980, all the years had different degrees of occurrence, with a slight loss of 10-20% of the paddy years, of which 1959, 1964 and 1974 occurred in large quantities, Serious damage, big loss. Especially in early or late rice that did not prevent or control ineffectiveness in 1974, the white spike rate is generally 20-30% and severe, reaching 50-70%. However, since 1976, the stem borers have been declining year by year. Especially since 1980, the generation of stem borers has been very small and the damage is very slight. Generally, the dry and white spike rates are both below 1% Great economic loss. The main reason for its occurrence is minor? And what are the most important farming and farming systems, comprehensive preventive measures to change the relationship more closely? Now try to analyze the following: