STUDY ON THE CONTROL OF HEMIBERLESIA PITYSOPHILA TAKAGI BY PRUNING AND THINNING

The paper emphatically expounded the effectiveness of the control of Hemiberlesia pitysophila Takagi by pruning and thinning of the young plantations of Pinus massoniana. During 1986-1988, we conducted an experiment of pruning and thinning in a 8-9-yearrold young pine plantation which covered about two hundred ha in Nianzhan forest district of Huidong County.The results have revealed that one third to one half population of H. pitysophila in the tree crown could be directly cleared off from the forest by pruning and thinning. In the stands with a canopy density of 0.5-0.7 |the insect population was 24-32 percent lower than that of the check plot (0.9 canopy density) and 30-60 percent of the mean pregnant egg number per female was reduced in the same year. Thus, the trees grow fast and the mean volume per tree is increased by 0.71-2.88 times as against the check. Besides, the mean economic income from pruning and thinning is about 1650 yuan per ha. Therefore, a reasonable pruning and thinning are an effective measures in the integrated control of H. pitysophila.