Abstract: [Objective] This study aims to evaluate the parasitic effects of Dastarcus helophoroides on Monochamus alternatus,and to explore the most cost efficient way to control the pest by the parasitoid.[Method] D. helophoroides eggs were released on the M. alternatus larvae and pupae of the infested bait-trees in pine forests with three ratios of the parasitoid and pest (5:1、10:1 and 15:1) to study the best releasing rate, and released eggs in six different periods to research the best releasing period, and in addition, released eggs in six different plots in Jinchuan forestry station Xingan County of Jiangxi Province to study the control effects of M. alternatus by D. helophoroides eggs in large tracts of land.[Result] The result showed that when the D. helophoroides eggs were released at the ratio of 15:1(eggs to beetle) on both the bait-tree logs in doors and the standing bait-trees in pine forests, the parasitic rate of D. helophoroides parasitic on M. alternatus was 85.17% and 82.20%, respectively. In the field experiments, the eggs were released in early-March, late-March, early-April, late-April, early-August and late-October in Xingan County respectively, and it was found that there were significant differences in the parasitic rates and among the releasing times, and early-April was the best time, and the reducing rate of M.alternatus was 82.37%. When mass releasing of eggs at a quantity of 4 000 per bait-tree, the controlling effect of M. alternatus reached to 58.04%-87.39%.[Conclusion] The result reveal that the releasing of D.helophoroides eggs is considerably effective to reduce M. alternatus populations, and the egg-releasing should be carried out in early April in the middle of Jiangxi province, and about 10 days earlier in the south and later in the north.

Key words: Dastarcus helophoroides egg, biocontrol, Monochamus alternatus, controlling effect