Classical biological control of the brown marmorated stink bug (Halyomorpha halys) in apple orchard: a success story.

Background: The brown marmorated stink bug (BMSB), Halyomorpha halys, is an invasive pest from eastern Asia that has caused significant damage to apple orchards in Europe and the United States. To reduce pesticide reliance, a classical biological control (CBC) program, using the Asian egg parasitoid Trissolcus japonicus, was initiated in Trentino, a key apple-producing area in Italy. The CBC program involved the release of T. japonicus at selected sites with minimal chemical input from 2020 to 2023. Monitoring was conducted to assess parasitoid establishment and egg parasitization rates. Preliminary data on fruit damage were also collected to assess trends at a large territorial scale. Parasitoid efficacy was evaluated based on discovery efficiency and parasitization impact.

Results: Trissolcus japonicus was recaptured in 62.3% of the sites, with increasing recapture rates over the years (from 30% in the first year to 65.4% in the fourth year). The overall egg parasitization rate increased from 18.3% to 50.6%, with T. japonicus contributing significantly (from 7.9% in 2020 to 41.3% in 2023). The percentage of hatched eggs decreased from 61.6% to 29.0%. Discovery efficiency improved from 9.9% to 54.4%, and impact from 7.9% to 39.0%. Fruit damage monitoring indicated an overall decreasing trend in orchards within a 2.5 km radius of successful release sites.

Conclusion: The release of T. japonicus in Trentino demonstrated effective control of BMSB, reducing pesticide use and fruit damage, thereby highlighting the potential of CBC as a sustainable pest management strategy against invasive alien pests. Further long-term studies are recommended to optimize and expand this approach. © 2025 The Author(s). Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.