Commercial development of plant essential oils and their constituents as active ingredients in bioinsecticides Murray B. Isman Received: 16 April 2019 / Accepted: 22 October 2019 Ó Springer Nature B.V. 2019 Abstract Insecticidal action of plant essential oils has been an area of intensive research in the new millennium, according to a recent bibliometric anal- ysis. Despite this overwhelming research effort, commercialization of bioinsecticides based on essen- tial oils has lagged far behind, although such products have now been used in the USA for over a decade, and in the EU in the last 4–5 years. Recent progress in commercialization of these products is reviewed here. Essential oils and their mono- and sesquiterpenoid constituents are fast-acting neurotoxins in insects, possibly interacting with multiple receptor types. These compounds also display potentially important sublethal behavioural effects in pest insects, including feeding and oviposition deterrence and repellence. Synergy among essential oil terpenoids appears to be a common phenomenon, and a mechanism for this action in rosemary oil has recently been demonstrated. Commercial development of bioinsecticides based on plant essential oils can follow several different path- ways producing products with active ingredients differing in their genesis. These include products whose active ingredients consist of (1) a mixture of essential oils; (2) a single essential oil, or a single terpenoid constituent; (3) a blend of terpenoids, synthetically produced, that emulate those in a plant essential oil; and (4) a novel (non-natural) blend of terpenoids obtained from different plant sources. Examples of each of these are provided. Keywords Natural insecticides Á Insecticidal terpenoids Á Feeding deterrents Á Oviposition deterrents Á Synergisitic natural products Introduction Judging by numbers of published scientific papers, interest in the potential use of plant essential oils or their derivatives for pest management—as bioinsecti- cides and/or as deterrents—has grown enormously in the past two decades. According to recent bibliometric analyses, more papers have been published in recent years on this group of natural insecticidal materials than on any other types or chemical classes of plant- derived natural products (Isman and Grieneisen 2014). Over the past 5 years, an average of 350 papers per year have been published on bioactivity of essential oils to insects (Grieneisen and Isman 2018). There are also numerous published reviews of this subject (Isman 2000; Koul et al. 2008; Regnault-Roger et al. 2012; Pavela and Benelli 2016; Walia et al. 2017), however most of these ostensibly review research reporting on the bioactivity of certain essential oils and/or their terpenoid constituents to insects through screening studies conducted in the laboratory. In M. B. Isman (&) Faculty of Land and Food Systems, University of British Columbia, Vancouver V6T1Z4, Canada e-mail: murray.isman@ubc.ca 123 Phytochem Rev https://doi.org/10.1007/s11101-019-09653-9