水稻瘤矮病的发病规律及防治研究

 水稻瘤矮病主要为害晚季稻,尤以杂优稻受害特重,这与杂优稻秧苗田播种量和大田插植苗数较少有关。目前病区未有免疫或高抗品种。早季稻一般受害较轻,仅零星发病,但成为晚季稻的主要侵染源。晚季稻播种后从秧针期开始(播后4-5天)即受侵染。特别是在7月中旬早季稻收割时介体叶蝉被迫大量迁移,秧田的虫数激增,秧苗感染率也激增。愈靠近早稻病田的秧苗感染率愈高。早播早植比迟播迟植发病重。秧苗在6叶龄前最易感染发病,苗龄愈小受害愈重,9叶龄后感染的不发病,所以大田的发病率基本上就是秧苗期的感染率。
防治本病主要抓晚稻秧田下述两项措施:(1)播植期适当推迟7-10天,即在7月中旬播种,8月上旬移植;(2)秧苗田从秧针期开始每4-5天喷药1次,共4-5次,如结合迟播则只需喷药2-3次。1983年的2,670亩防治试验和1984年病区全面推广防治结果,防效极为显著。1984年发病面积仅3.36万亩,为1982年发病面积50万亩的6.7%;发病率在0.5%以下,(1982年一般发病率为20-30%,严重的达98%)基本不造成为害,保产约2,500万公斤。

ON THE EPIDEMIOLOGY AND CONTROL OF RICE GALL DWARF IN GUANGDONG

The rice gall dwarf disease in the epidemic districts in Guangdong prevailed chiefly in the fall crop of rice,especially the hybrid varieties due to much smaller quantity of seeds sown in a given area of nursery plot and much smaller population density of plants as compared with ordinary varieties.There were no immune Varieties observed.The disease was not important at all in the spring crop,but the crop infected in spring served as the source of inoculum for the fall crop.A few weeks before the spring crop was harvested,the fall crop had already started,and right after the germination of the seeds infection might take place.The infection rate in the nursery reached its peak right after the harvest of spring crop when the vector insects were forced to migrate from the spring crop.The closer the nursery to the spring crop fields,the higher the infection rate,however,the highest ones were located within a distance of 10-16 meters.Earlier sowing and earlier planting also gave higher infection rate.Rice seedlings were susceptible to the disease only before 8-leaf stage and were susceptible at and before 6-leaf stage;the seedlings infected at 9-leaf stage or older never showed any symptoms.Thus the disease incidence in the field throughout the whole season was practically the same as that in the nursery.
According to the epidemiology of the disease mentioned above,the disease was rather easily and effectively controlled by applying the following 2 measures:(1) The seed-sowing date of the fall crop,especially the hybrid varieties,was properly postponed for 7-8 days to middle of July,and the transplanting date to early August;(2)Insecticide was applied once every 4-5 days at and after needle-leaf stage of the seedlings.In case of postponing seed sowing date,2-3 applications might be sufficient.These measures were found very effective according to the results of the experiment in 2,670 mu^* in 1983 and were then extended to all the diseased districts or counties in Guangdong province in 1984,resulting in a reduction of diseased area from more than 0.5 million mu in 1982 to only 33,600 mu in 1984 and of disease incidence from 20-30% in average to less than 0.5% in the same period of time.A gain of 25 million kg of yields was estimated.