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Chinese Journal of Biological Control ›› 2022, Vol. 38 ›› Issue (3): 587-594.

• RESEARCH REPORTS •

### Parasitic Effect of Dastarcus helophoroides of Monochamus alternatus Biotype on Monochamus saltuarius

ZHENG Yanan1, WANG Jue1, WANG Weitao1, LI Yang1, FAN Lichun1, SHI Yong1, ZHANG Yanlong2

1. 1. College of Forestry, Shenyang Agricultural University, Shenyang 110866, China;
2. Ecology and Nature Conservation Institute, Chinese Academy of Forestry/Key Laboratory of Forest Protection of National Forestry and Grassland Administration, Beijing 100091, China
• Received:2021-05-19 Published:2022-06-20

Abstract: Monochamus saltuarius is a major vector of Bursaphelenchus xylophilus, the pathogen of the pine wilt disease,in the middle temperate zone of China, biological control of the vector is important for control of the pine wilt disease. M. alternatus is the major vector of B. xylophilus in South China. Although Dastarcus helophoroides is an effective parasitoid of M. alternatus, there are no reports of the management of M. saltuarius by D. helophoroides. The control effect of D. helophoroides on M. saltuarius was tested in the laboratory and forests. To determine the optimal timing of parasitoid release and the ratio of parasitoid to pest, D. helophoroides larvae were inoculated to M. saltuarius in different developmental stages in the laboratory, and D. helophoroides eggs were released to the cut logs of Pinus koraiensis infested by M. saltuarius in different ratios of parasitoid to pest to simulate the natural conditions. Under natural conditions in the forest, D. helophoroides eggs were released to the cut logs of P. koraiensis infested by M. saltuarius at different ratios of parasitoid to pest. The results showed that, the average number of D. helophoroides larvae parasitizing on M. saltuarius was 3.10/pupa, the average parasitism rate was 86.00%, and the average survival rate of D. helophoroides was 57.79%. When the host was M. saltuarius, the corresponding data were 0.54/larva, 30.00%, and 13.92%, respectively. In the laboratory, D. helophoroides eggs released to the cut logs of P. koraiensis infested by M. saltuarius at a parasitoid to pest ratio of 10:1 achieved the highest parasitism rate of 42.59% and the highest corrected host mortality of 40.71%. In forests, similar operation achieved the highest parasitism rates of 47.68% at a parasitoid to pest ratio of 4:1 and of 45.51% at a ratio of 2:1, which were not significantly different. The operation saw the highest corrected mortality of M. alternatus of 74.15% at a parasitoid to pest ratio of 10:1, not significantly different from that obtained at a ratio of 2:1, and an average parasitism rate of 33.38%, lower than that obtained at a ratio of 2:1. In conclusion, D. helophoroides of M. alternatus biotype performs better on M. saltuarius pupae than on M. saltuarius larvae, indicating the pupal stage is a suitable stage for control of M. saltuarius. The laboratory and forest tests show that D. helophoroides can be used to control M. saltuarius. Release of D. helophoroides eggs to control M. saltuarius in forests is cost-effective at the parasitoid to pest ratio of 2:1.

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