Effects of Fourth-generation Cnaphalocrocis medinalis on Rice Yield and Control Index

[Objective] The aim was to find out effects of fourth-generation Cnaphalocrocis medinalis on rice production in Yangzhou District and its control index.[Method] Through artificial control of insects in field,4 different insect volume gradients were set,the effects of different Cnaphalocrocis medinalis amounts on leafroll rate and yield loss of Wuyunjing No.23 were determined.[Result] The results showed that within the range of 0-20 head/hole,with increasing of insect amounts,rice yield decreased,leafroll rate and rice yield loss rate increased.According to 3% economic permit loss rate,the control index of Cnaphalocrocis medinalis on Wuyunjing No.23 was 173 head/hole.[Conclusion] The study will provide theoretical basis for effectively control fourth-generation Cnaphalocrocis medinalis in Yangzhou District.