稻纵卷叶螟为害的产量损失与防治指标

1979—1983年作者探讨了稻纵卷叶螟Canphalocrosis medinalis为害的产量损失和防治指标,通过大田调查,控虫观察与模拟试验后,肯定剑叶被害后减产9.3—20.3%(秈稻)和10.7—15.6%(杂交稻);全部叶片被害后减产26.5—36.7%(秈稻)和30.2—44.3%(杂交稻)。其减产程度是抽穗期>分蘖期>乳熟期。而防治指标因稻生育期不同:分蘖期为丛平均有三龄幼虫0.75—1.4条;抽穗期为平均0.5—0.7条。在天敌少时采用指标的上限,反之,使用下限。抽穗期是防治关键。生长嫩绿的稻田是防治的重点对象。这些指标曾在五万余亩稻田示范后,功效十分显著。

YIELD LOSS OF RICE CAUSED BY RICE LEAF ROLLER AND THE THRESHOLD OF ECONOMIC INJURY

The reci leaf roller Cnaphalocrosis medinalis has become a serious pest on rice in Henan Province since 1970. We have studied the yield loss of rice caused by this insect and the threshold of economic injury for five years. The results of this study can be summarized as follows:1.With the same population size of the pest the yield loss of rice varies with the developmental stages of the rice crop, being heaviest at the early earing stage, medial at the tillering stage, and least at the milky-seed stage.2.The injury percentage of rice foliage, the area of foliage lost and the yield loss of rice are correlated with the population size of the pest and the relationship holds true at all the three stages of vegetative growth.3.The threshold of economic injury caused by the insect will be 0.75 to 1.4 catepil-lar (in the third instar) per hill at the tillering stage and 0.5 to 0.7 caterpillar per hill at the early earing stage. The upper limit should be adopted when natural enemies of the pest are scarce and the lower limit adopted when natural enemies in abundance. The early earing stage is considered to be the most vulnerable stage and darkgreen rice fields the main targets of control.