The Forecast Model for the Occurrence of Forth Generation of Larva of Leaf Roller of Rice(Cnaphalocrocis medinalis)in Yuqing County

The data from 1993~2004 of rice leaf folder in Yuqing county were analyzed for discovering the occurrence period of 4th generation larva,the regression equation for the occurrence of the 3rd and 4th generation larva is y=3.1293+0.8776x±Sy=2.951,r=0.730r_((0.01,10))=0.708~(**),the regression equation for the peak stage of 4th generation of adults in the field and 4th generation larva is y=-1.2483+0.6729x±Sy=2.472,r=0.923r_((0.01,10))=0.708~(**).It is easy and accurate to forecast the peak stage of 4th generation of adult and the 4th generation of larva by using the regression model.