Unintentional biological control

Authors: Weber, Donald; HAJEK, ANN - Cornell University; Hoelmer, Kim; SCHAFFNER, URS - Commonwealth Agricultural Bureau International (CABI) - Switzerland; MASON, PETER - Agri Food - Canada; STOUTHAMER, RICHARD - University Of California; TALAMAS, ELIJAH - Florida Department Of Agriculture; Buffington, Matthew; HODDLE, MARK - University Of California; HAYE, TIM - Commonwealth Agricultural Bureau International (CABI) - Switzerland

Submitted to: Book Chapter
Publication Type: Book / Chapter
Publication Acceptance Date: 3/2/2020
Publication Date: N/A
Citation: N/A

Interpretive Summary: Invasive insect species are a huge problem for the United States and many other countries, costing billions of dollars per year in agricultural and forest losses and added control costs, as well as medical and veterinary threats. One strategy to deal with these exotic pests (which are typically from other continents) is to discover natural enemies, organisms that suppress the pest, in their original ecosystems. This process of “introduction biological control” is highly regulated, to avoid mistakes such as importing natural enemies which attack non-target or beneficial insects, or importing natural enemies with their own enemies including pathogens. There is good reason to regulate this selection process. However, there are a number of recent examples of natural enemies, including parasitoids (parasites that kill their host) such as tiny wasps that attack pest insect eggs, insect pathogens such as fungi, and even beneficial weed-eating insects, jsutshowing up and becoming established as a result of unintentional introduction. Sometimes this has resulted in control of the pest, but this is not always the case. This presentation discusses the phenomenon of unintentional introductions of natural enemies, in what ways the results could be positive or negative, what ways in which they likely have been introduced, and what the options are for restricting their inflow, compared to the already high scrutiny accorded to proposed intentional introductions. This book chapter is likely to be of interest to pest managers, researchers, regulators and other stakeholders impacted by, or otherwise involved with invasive pests.

Technical Abstract: Accidental introductions of natural enemies, including parasitoid and predatory groups, exceed species introduced intentionally. Several factors favor this: a general surge in international trade; lack of surveillance for species that are not associated with live plants or animals; inability to intercept tiny organisms such as scelionid parasitoids or entomopathogens; huge invasive host populations in source and/or receiving areas that allow rapid establishment; and lack of aggressive screening for pests already established. This book chapter reviews the available databases for non-native fauna in several continents and islands, contrasting proportions due to intentional versus unintentional introductions in particular for parasitoids in the order Hymenoptera. We also profile a number of recent frequent and surprisingly rapid accidental natural enemy introductions, including insect parasitoids, pathogens, and insect herbivores of invasive weeds. These examples raise important issues of the role of systematics and genetic considerations for unintentional introductions, and also call into question the regulatory emphasis on a rigorous and protracted process for introduction (classical) biological control, when adventive unintentional introductions have a high probability to displace or disrupt this planned process.