Abstract: In order to determine when and whether or not controlling D. punctatus with chemical, the effects of artificial defoliation and the caterpillar larvae have been studied. The results are as follows:There is no significant effect between artificial and natural defoliation for the volume growth rate. If the tree is defoliated to 70% or more, there is significant as compared with those non-defoliated. And if the tree is defoliated nearly 100% duririg the August or September, nearly 25 percent of trees died and the percentage of volume is lowering to 31% of the normal. In general,the trees injured heavily (?)y the pest recover at third year.The control threshold tables are developed as following empirical formula:CT = A(1293.4D + 4684.5C-626.2H-4088.5)/14.20where, CT = the larvae density that can be controlled with the chemicals, D = the diameted breast high (cm.) of the tree; H = the height (m.) of the tree;C = the ratio of the crown length/height of the tree; A = the degree of the defoliated from 10%to 90% ; 14.20 = a constant destruction by a single larva.