Abstract
The contributions in this Special Issue originate from a Symposium "Classical biological control of weeds and arthropods: Evaluation of social, economic and ecological benefits" presented at the 26th International Congress of Entomology, held in Helsinki, Finland in 2022. Following an opening article analyzing agent and target traits associated with greater success odds in weed biological control, a perspective article summarizing how biological control programs are currently assessed and how they may be evaluated going forward frames the articles in the Special Issue. Articles assess different dimensions of success for selected weed and arthropod biocontrol programs either on the individual project level or through summaries of recent projects for geographic regions. Success dimensions include economic, ecological and socio-economic benefits. Included are also several articles that summarize or propose the use of innovative tools to improve biological control as a discipline going forward. Overall, this Special Issue portrays a status quo of biological control characterized by thoughtful analyses of project outcomes and recommendations to improve outcome assessments and increase the odds of success. As such, an optimistic prognosis for biological control is provided.