Abstract: Researches on the influence of different felling intensity and different ways to exploit and utilize tropical secondary forest in Hainan Island on soil microbial activity showed that the total quantity of soil microorganism and activity of soil enzyrnes gradually drop down as the felling intensity rise.All activity indexes are lowest in the treatment of clear felling and are significantly higher in rubber plantation than in slash-and-burn cultivation.It ls suggested that 50% exploitation and strip cropping of rubber would be the reasonable utilization ways if only soil microbial activity are considered.

Key words: Frankliniella occidentalis Pergande, phoxim, cross-resistance, resistance mechanism.