水稻褐鞘症发生原因的进一步探讨

为进一步探讨水稻褐鞘症的发生原因,本试验设室内人工接种和室外田间小区喷药防治两项处理。人工接种分设接螨、接菌、接螨加接菌和对照4个处理组;田间小区喷药防治则分设喷杀螨剂(双甲脒)和杀菌剂(多菌灵、井岗霉素)两个处理组。获得如下结果: 1.接螨组和接螨加接菌组的病株率分别为89.54％、99.14％;病情指数分别为57.84、38.86;单株带螨量分别为20.74头、12.6头(均包括卵粒)。接菌组和对照组的病株率分别为31.98％、15.36％;病情指数分别为5.98、2.91;单株带螨量分别为1.85头、0.06头(均包括卵粒)。 2.田间喷施杀螨剂(双甲脒)小区比喷施杀菌剂(多菌灵)小区螨发生期推迟15天,单株带螨量降低(分别为18.5头、8.2头)、防治效果较高(分别为51.8％、29.46％)。以上证明斯氏狭跗线螨(Steneotarsonemus spinki Smiley)为华南地区水稻褐鞘症发端的祸首,只要防螨得宜,稻褐鞘症也就可大为减轻。

FURTHER STUDIES ON THE CAUSE OF RICE BROWN SHEATH IN SOUTH CHINA

A series of experiments, including artificial inoculation and pesticide control in the field were conducted for clarifying the cause of rice brown sheath in South China. The indoor artificial inoculation treatments were:(1) rice tarsonemid mite, Steneotarsonemus spinki Smiley only; (2) sheath rot fungus, Sarocladium oryzae (Acrocylindrium oryzae); (3) tarsonemid mites plus sheath rot fungus and (4) check. The field pesticide control treatments were:(1) spraying insecticides and (2) spraying fungicides.The results were summarized as follow:1.Rice plants infested with tarsonemid mites showed a singnificant increase in the percentages of diseased rice plants, disease index and numbers of tarsonemid mites per rice plant when compared with treatments of fungi and check. Similar result was also found in treatment of mites plus fungi.2.The occurrence of rice tarsonemid mites in the treatment of spraying insecticides was 15 days later than in the treatment of spraying fungicides. The numbers of tarsonemid mites per rice plant in former treatment were less than that in latter treatment and the effects of controlling the rice brown sheath in former treatment were higher than that in latter treatment. It is concluded that the rice tarsonemid mites play a major role in causing rice brown sheath in South China. So long as improved measures for controlling tarsonemid mites are adapted, the rice brown sheath will be reduced greatly.