Abstract: Based on the effect of natural defoliation of pest insects on the growth of poplar tree,an artificial defoliation has been made to observe the influence of this treatment on poplar tree's growth.The results obtained are as follows: 1. There was no significant effect of artificial defoliation 25% and 50% on the growth in diameter and in height,as compared with the control.However,a defoliation of 75% and 100% resulted in the decrease of 21.2% and 50.8% in diameter and 20.5% and 44.7% in height of the tree tested,respectively. 2. The average amount of leaves eaten by a single Clostera anachoreta (Faby.) from the first generation to the fourth generation was 15935mn²,8184mm²,10226mm²,14168mm²,respectively.