Natural and released inoculum levels of entomopathogenic fungal biocontrol agents in soil in relation to risk assessment and in accordance with EU regulations

Entomopathogenic fungi being developed as biological control agents (BCAs) may have the potential to spread and become established in the environment. For registration purposes, the risks concerning their persistence have to be evaluated according to EU legislation which requires the decline of BCAs to acceptable background levels unless related risks are acceptable. In order to deal with this requirement, applicants of a BCA need to give information on its persistence and natural background levels. For risk assessors and registration authorities guidance on how to evaluate data on natural background levels of indigenously occurring species (= same species as the introduced BCA) is needed. For this purpose, an overview is presented on background levels of some indigenous fungi as well as persistence data of some applied fungal BCAs. Data were restricted to commerical species. It was found that for the species Metarhizium anisopliae, Beauveria bassiana and Beauveria brongniartii natural densities were relatively low and introduced strains of these fungi decreased gradually in time. Many factors were found in the literature, such as intrinsic, edaphic, biotic, climatic, and cultural factors, that could explain this decline.