Study on the Forecast Technique and Control Index of Larch Caterpillar of A Cycle in Two Years

This article deals with the correlation among the occurrence period of Dendrolimus superans (Butler),phenology and 24 solar terms as well as its occurrence amount,warm rain coefficient in May and overwintering larva′s shit in Yakeshi forest destrict from 1993 to 1995. We set up the regressive estimate model of the volume of occurrence (y):ŷ =196.268 0-23.517 0x1,ŷ(larva)=2.449 9+0.073 2x2,ŷ(adult)=11.970 0+0.027 8x2,in which the warm rain coefficient and larva′s shit act as dependent variable. The reasearch proves that it makes a great differencc to the height,the chest diameter and the volume of tree when loss amounts of Larix gmelinii leaves go beyond 45 percent in the total. Before the middle of May,the numbers of the trees which have insects is over 40 percent of the total trees,and the mature larvae adult insect density in each tree is over 50 heads and the young larvae density is over 101 heads,control measure should be adopted.