Plant-Derived Insecticides Under Meta-Analyses: Status, Biases, and Knowledge Gaps

Abstract

Plant-derived or botanical insecticides are biopesticides experiencing substantial ongoing increase in interest. The 74 years of our literature survey tracked over 2500 papers on botanical insecticides published between 1945 and 2019 (Web of Science database). Such a survey allowed meta-analyses to recognize current status and biases of the studies providing important insights into the research topic. They include the recognition of the exponential growth of such studies since the 1990s, the prevalent interest on the Meliaceae plant species and a dozen additional families, although some 190 families have been investigated. The arthropods targeted by such studies were pest species (ca. 95%) with rather little attention devoted to non-target species (p < 0.001). This bias is followed by another one—mortality assessments are prevalent among target and non-target arthropod species when contrasted with sublethal assessments (p < 0.01). These omissions are pivotal, as they fail to recognize that sublethal effects may be as important or even more important than mortality, and that initial insecticide deposits quickly degrade over time leading to prevailing sublethal exposure. Furthermore, although the target of control is limited to few species, non-target species will be exposed and as such need to be factored into consideration. Thus, these biases in studies of botanical insecticides incur in knowledge gaps with potential consequences for the practical use of these compounds as pest management tools.

Representative Farm-Based Sustainability Assessment of the Organic Sector in Switzerland Using the SMART-Farm Tool

“…While overall risk levels were low (only 16 PM farms showing moderate to high risk levels, i.e., scores of 2 or 3), the issue does deserve attention. While OA forbids the use of synthetic pesticides, organic, plantbased alternatives also have harmful active substances, and a process of simple input substitution will not necessarily improve environmental outcomes (Bahlai et al, 2010;Smith and Perfetti, 2020;Turchen et al, 2020). Finally, the number of days of absence due to occupational injury was influential for all farm types, with an average value of 3.22 and a maximum value of 70 days per year and FTE (data not shown).…”

Sublethal exposure to an emulsion based on Pogostemon cablin (Lamiaceae) essential oil impairs digestibility, feeding, fecundity, and mobility of the coffee berry borer, Hypothenemus hampei

“…The advantages of EO-based emulsions for the development of eco-friendly insecticides include: (i) reduction in EO particle size; (ii) delayed release of active ingredients in the environment; and (iii) increased EO penetration in the insect body (Athanassiou et al 2018;Pavoni et al 2020). Nevertheless, plant-based insecticide, such as EO, have been evaluated mainly regarding their acute toxicities, while sublethal effects are often overlooked (Turchen et al 2020).…”

Aqueous and Ethanolic Plant Extracts as Bio-Insecticides—Establishing a Bridge between Raw Scientific Data and Practical Reality

“…In recent years, various works have been carried out to ascertain whether some plant extracts have the insecticide potential to become a reliable choice over synthetic insecticides, with some of them showing very interesting results [ 47 , 53 ]. The bibliographic research carried out revealed some works whose experimental design, activity level and/or conclusions deserve a more detailed discussion, being presented below.…”