Efficiency Enhancement Technology of Dastarcus helophoroides (Coleoptera: Bothrideridae) for Controlling Monochamus alternatus (Coleoptera: Cerambycidae): Drilling Optimization and Biological Collaboration.

Dastarcus helophoroides Fairmaire, a parasitic natural enemy widely used in the biological control of Monochamus alternatus Hope, possesses strong abilities to search for hosts and prey. To enhance the biological control efficacy of D. helophoroides against M. alternatus, this study systematically evaluated the effectiveness of enhancing control through methods such as drilling holes in lure logs and introducing D. helophoroides carrying Pyemotes zhonghuajia or Beauveria bassiana under controlled indoor conditions. The results showed that: (1) Releasing D. helophoroides eggs (after 30 days) and releasing adults (after 120 days) were both effective in controlling M. alternatus, with the best control effects achieved when 50 eggs/m and 3 adults/m were released. The release of adults took longer to show effects but had better results than the release of eggs in the later stages. (2) The location and number of holes drilled in lure logs significantly influenced the efficiency of D. helophoroides in searching for and parasitizing M. alternatus, while the diameter of the holes was not significant. Considering the highest control efficacy and minimizing damage to the tree, the optimal conditions were releasing D. helophoroides adults 2 cm above M. alternatus fecal holes, with 0.4 cm in diameter and 2 holes/m release density, which significantly promoted the invasion of D. helophoroides adults into the borer tunnels and increased the M. alternatus mortality rate. (3) Releasing D. helophoroides adults carrying P. zhonghuajia or B. bassiana significantly improves the control efficacy against M. alternatus. The higher the number of D. helophoroides adults released per log segment and the greater the quantity of P. zhonghuajia or B. bassiana that they carry, the higher the mortality rate of M. alternatus. After 60 days of release, the highest mortality rate of M. alternatus was observed in treatments where D. helophoroides (released at densities of 3 adults per meter of log segment) carried P. zhonghuajia (0.6 million/m) or were sprayed with B. bassiana (3 g/m). The synergistic effect of carrying P. zhonghuajia was evident, but the overall control efficacy of spraying B. bassiana was limited. In summary, optimizing drilling techniques and combining biological release strategies under laboratory conditions can significantly enhance the control efficacy against M. alternatus, providing data support for D. helophoroides future application in forest pest control.