The occurrence, damage and action threshold of Chinese rice grasshopper,Oxya chinensis, in rice field

صينى. 系统地研究了中华稻蝗发生动态与危害损失。结果表明，中华稻蝗在浙江年发生1代，主要危害早稻和早播单季晚稻。水稻分蘖期接入虫量10～50头/ m2，叶被害率为52.61%～78.81%，叶被害指数为14.51～25.00，产量损失率为2.31%～27.42%，孕穗至破口期接入虫量1～17头/m2，叶被害率为56.63%～88.00%，叶被害指数为14.69～31.32，产量损失率为1.28%～32.74%，随着虫口密度增加，危害程度上升，产量损失率加大，两者具有密切相关性，建立了危害损失关系式。水稻叶片受害、光合能力减弱、幼穗分化不良、实粒减少、秕谷增加和粒重下降是导致水稻减产的主要原因。模拟测试表明，随着水稻受害生育期推迟损失增大，且分蘖期危害具有一定的补偿能力。在现有生产条件下，经济允许损失水平为2.5%～3.0%；2～3龄蝗蝻为防治适期，氟虫腈、三唑磷等有较好防治效果。提出水稻分蘖期和孕穗至破口期防治指标分别为10头/m2和5头/m2。

إنجليزي. The Chinese rice grasshopper (CRG, Oxya chinensis) occurs one generation a year in Zhejiang Province, it mainly damages on early rice and early planting single late rice in the middle and lower reaches of Yangzi River Valley. There were close relationships among population densities of CRG (at tillering, ear bearing-early heading stages) and damaged leaf rate, leaf injury index, and yield loss rate of rice; the harmfulness and yield loss rate of rice increased with the population of CRG. After the damage of CRG, the intensity of photosynthesis of rice plant was weakened, its young panicle differentiation was abnormal, grain setting rate decreased, blighted grain number increased, and grain weight reduced, all of these were main causing factors of rice yield reduction. The simulation injury test showed that the rice plant at tillering stage has rather strong compensation ability against the damage of CRG, and then the yield loss increased with the delaying of injury test stage. The tolerable rice yield loss level was determined as 2.5%-3.0%, the suitable stage of CRG for spraying were 2nd-3rd instar nymphs, the action thresholds at tillering and ear bearing-early heading stages were 10 and 5 nymphs per square meter respectively. Fipronil and triazophos were recommended as the desirable insecticides for CRG control.