Abstract: With rice varieties Jiahua 1 (resistant to the white backed plant hopper Sogatella furcifera) and Shanyou 63 (susceptible) as test materials, this paper studied the effects of different insecticide treatments on the pest population and quality and yield of rice grain, and evaluated their actual economic benefits (AEB). The results indicated that in the control plot, the peak density of S. furcifera on Jiahua 1 was only 1/10 of that on Shanyou 63. Throughout the whole rice growth period, the S. furcifera population on Jiahua 1 kept below economic injury level, while Shanyou 63 suffered heavy infestation by S. furcifera. The spider density in the control plot was 3～7 times higher than that in the plots treated with insecticide following farmers’ practice. No application of insecticide decreased the grain yield of Jiahua 1 and Shanyou 63 by 11.8% and 43.4%, respectively. Compared with the control, spraying with insecticide one time decreased the AEB of Jiahua 1 and Shanyou 63 by 0.9%～2.6% and 2.6%～4.7%, respectively. Without insecticide application, the AEB of Shanyou 63 decreased by 32.9%～36.1%, while that of Jiahua 1 increased by 2.2%～4.8%. The income of planting Jiahua 1 without insecticide application was 9403 yuan·hm^-2, which was remarkably higher than that (8632 yuan·hm^-2) of Shanyou 63 protected by spraying insecticide 3 times. It was worthwhile to point out that insecticide treatment did not affect the processing of rice grain and its commercial and edible quality, but decreased its protein content of Jiahua 1 and Shanyou 63.

Key words: Changbai Mountain, Plant community, α diversity, Altitude gradient