Beauveria bassiana (Ascomycota: Hypocreales) spores carried by Scleroderma guani (Hymenoptera: Bethylidae): a novel strategy for improving the control efficiency of Semanotus bifasciatus (Coleoptera: Cerambycidae) in the field

One common biocontrol strategy employed to combat the wood borer Semanotus bifasciatus Motschulsky (the Chinese fir borer, CFB) is the release of parasitic wasps, specifically Sclerodermus guani Xiao et Wu. However, the rate of parasitism of these wasps is not sufficient to meet the increasing demand for effective control. To address this issue, the present study explored the potential of releasing parasitic wasps carrying spores of the entomopathogen Beauveria bassiana. Vuill. BD01 (Bb@Sg) to enhance the control efficacy against CFB. Administering spore powder on the wasp bodies retained more spores compared with using spore suspensions. Releasing parasitic wasps in a CFB to S. guani ratio of 1:3 resulted in higher rates of parasitism compared with ratios of 1:2 or 1:4. In addition, the Bb@Sg strategy resulted in a mortality rate of 91.55% at day 90 against CFB in a laboratory biocontrol experiment using cypress (Juniperus chinensis L.), being 16.24–19.30% more effective than using only S. guani. Promising results were also observed in the field, where the mortality of CFB in cypress trunks reached 83.36%, 11.62% higher than the rate obtained solely from S. guani release. This study introduces a novel biocontrol strategy for CFB and advances our understanding and application of joint strategies against longhorned beetles and other wood borers.