Classical biological control

Authors: BOROWIEC, NICOLAS - Inrae; SFORZA, RENE - European Biological Control Laboratory (EBCL)

Submitted to: Book Chapter
Publication Type: Book / Chapter
Publication Acceptance Date: 3/21/2022
Publication Date: 6/21/2022
Citation: Borowiec, N., Sforza, R.F., Talamas, E., Roche, M., Smith, L. 2022. Classical biological control. Extended Biocontrol. Springer. Chapter 3, pp. 31-42.

Interpretive Summary: Among today’s many biological control strategies, classical biological control (CBC) is the oldest – it dates back to the nineteenth century, which explains its name. This biological control method is based on the intuitive idea that fighting an invasive population requires finding a natural enemy from its native range. CBC is therefore closely linked to biological invasions for two reasons: first, because the main principle of CBC is to combat invasive insects or plants by introducing specific natural enemies from the same native range; and second, because introductions of exotic biological control agents for CBC can be considered a “planned biological invasion”, and therefore used to analyse the factors for establishment success and failure in introduced populations. Thus, the initial idea opens the door to a lengthy scientific, technological and sociological process. In this chapter, we will discuss the different stages of this process through selected examples. The starting point of this journey is the search for natural enemies of species considered harmful because they negatively impact crops. These natural enemies, or biological control agents, are considered “beneficial”; they are used for the benefit of human activities, while the fauna and flora of the invaded areas also benefit from this sustainable and environmentally friendly control method. We detail the different stages of this long journey, which goes from studying the literature on pests and potential biological control agents to field exploration and specimen collection. We will then discuss laboratory and natural condition assessments through recent examples.

Technical Abstract: The way CBC projects are implemented has hardly changed in 140 years. Raising the necessary funds to launch the project, surveying the pest’s native range, rearing potential biocontrol candidates and evaluating their specificity are still the key phases of any classical biological control programme today. However, the diagnostic tools now available to evaluate and verify the taxonomic and biological parameters of organisms (plants, insects, mites, pathogens) and various modes of transport have revolutionized the discipline. CBC is now a well-established plant protection approach. However, new projects require sufficient new technological, human and financial resources for up to 10 years, which can be an obstacle to implementation. This is all the more significant given that CBC operations are generally carried out by public research stakeholders with limited budgets, which means they must respond to calls for projects in an increasingly competitive environment. But while securing funding for CBC research is challenging, the benefits it brings to agriculture and the environment are real and should encourage public and private funding. In this chapter, we present and detail the recent case of the oriental chestnut gall wasp which is a perfect example. The pest, gall wasp Dryocosmus kuriphilus, which is native to China, first invaded Asia (Japan, Korea, Nepal) before colonizing other continents. After arriving in Italy in 2002, it took just 15 years for this insect to colonize the entire European chestnut production area. Surveys carried out in China by Japanese researchers led to the discovery of a parasitoid specific to oriental chestnut gall wasps: Torymus sinensis (Torymidae). Introductions of this parasitoid wasp effectively controlled pest populations in Japan in the 1970s; introductions of T. sinensis were then made in the USA. In Europe, T. sinesnsis was first introduced in Italy in 2005, with effective control of the pest achieved after eight years, followed by other European countries (France, Slovakia, Hungary, Portugal, Spain). In France, experimental introductions combined with postrelease monitoring showed that pest populations had stabilized below the damage threshold 5–6 years after the initial releases. The CBC programme also showed that T. sinensis had maximum success in establishment (100%), regardless of the tested introduction treatment. Through this example, the entire chapter presents the different steps required to achieve a biocontrol program by importation of specific natural enemies.