Abstract: Coccobius azumai Tachikawa which was introduced from Okinawa, Japan, was first released and successfully established in Huidong County, Guangdong Province in 1989.Since then systematic observation and investigation were made. The result showed that a year later the parasitism rate of C. Azumai on Hemiberlesia itysophila reached as high as 55.8%-64, 2% within 50m from the released site and the density of female H. pitysophila was reduced from 3.41 to 0.64 per needle. Two years later the effective control radius hadincreased to about 300m. The parasitism rate ranged from 20.8% to 32.9%. The density of female H. pitysophila became as low as 0.6 per needle. Both C. azumai and H. pitysophila were in a balanced state of Iow density, whereas in the areas where no C. azumai was released, the density of female H. pitysophila had increased from 3.4 to 4.22 per needle, 6.10 times higher than that in the released area. Judging from the spreading speed ,competitive ability and the number-stabilizing level of C. azumai, it is concluded that Marietta carnesi(Howard) had only a hyperparasitism rate of 3.1%45.3% so that it had no influence on the control efficiency of C. Azumai.

Key words: Coccobius azumai, Hemiberlesia pitysophila, biological control, efficiency