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经1987～1990年盆栽、小区和大田试验,结果表明褐稻虱和纹枯病对水稻孕穗期复合为害造成的产量损失主要表现在千粒重和结实率的降低。建立了复合为害产量损失预测式=0.08699+0.243521x_1+0.206998x_2。并将该预测式于1988～1989年进行了大田检验,结果经卡平方分析表明,符合大田实际褐稻虱和纹枯病复合为害产量损失,适用于预测。不同生育期水稻受害损失试验结果表明幼穗形成期至灌浆期受害,水稻产量均受到严重影响。在褐稻虱和纹枯病复合为害允许损失水平为3～5％时,防治指标定为:2～3龄若虫5～8头/丛,纹枯病病株率10～15％。
The results of pot experiment, plot experiment and field experiment from 1987 to 1990 showed that the yield loss caused by combined damage of brown planthopper and sheath blight on the booting stage of rice was mainly due to the decrease of 1000-grain weight and seed setting rate. The yield loss prediction formula of composite damage was established = 0.08699 + 0.243521x_1 + 0.206998x_2. The predictive formula was tested in the fields from 1988 to 1989. The results of the square analysis showed that the yield loss in line with the combined damage of brown planthopper and the sheath blight in the field was suitable for the prediction. The results of rice damage at different growth stages showed that the damage occurred during panicle formation and grain filling stage and the rice yield was seriously affected. When the allowable damage level of the combined damage of brown planthopper and the sheath blight was 3 ~ 5%, the control index was set as 5 ~ 8 nymphs of 2 ~ 3 instar nymphs and the rate of diseased plants of sheath blight was 10 ~ 15%.