Acute toxicity effects of pesticides on predatory snout mites (family Bdellidae)

Abstract

Predatory mites biologically control a range of arthropod crop pests and are often central to agricultural IPM strategies globally. Conflict between chemical and biological pest control has prompted increasing interest in selective pesticides with fewer off-target impacts on beneficial invertebrates, including predatory mites. However, the range of predatory mite species included in standardised pesticide toxicity assessments does not match the diversity of naturally-occurring species contributing to biocontrol, with most testing carried out on species from the family Phytoseiidae. Here, we aim to bridge this knowledge gap by investigating the impacts of 22 agricultural pesticides on the predatory snout mite Odontoscirus lapidaria (Kramer) (family Bdellidae). Using internationally standardised testing methodologies, we identified several active ingredients with minimal impact on O. lapidaria mortality, including Bacillus thuringiensis, nuclear polyhedrosis virus, flonicamid, afidopyropen, chlorantraniliprole and cyantraniliprole, which may therefore be good candidates for IPM strategies utilising both chemical and biological control. Importantly, we reveal differences between Bdellidae and Phytoseiidae in responses to a number of chemicals, including the miticides diafenthiuron and abamectin, highlighting the risk of making generalisations around acute toxicity based on tests with one beneficial mite family. We also explored the impacts of several pesticides on a second Bdellidae species and found differences in the response to chlorpyrifos compared with O. lapidaria, further highlighting the taxon-specific nature of non-target toxicity effects.

Acute toxicity effects of pesticides on beneficial organisms – Dispelling myths for a more sustainable use of chemicals in agricultural environments

“…We conducted acute toxicity assessments on 15 beneficial invertebrate species, spanning ten predatory and parasitoid insect and arachnid groups, including predatory mites, spiders, ladybirds, rove beetles, lacewings, hoverflies, predatory bugs, aphid parasitoid wasps, and lepidopteran egg and larval parasitoid wasps (Tables S1 & S2). Although selected because they are important beneficials of the Australian grains industry (see Overton et al 2021), many of these species are among the most important beneficials globally (Buitenhuis et al 2023) (Knapp et al 2023a). Female wolf spiders carrying egg cases or spiderlings were collected between spring and autumn of 2021 and 2022, and spiderlings were tested following dispersal from their mother's abdomen.…”

“…Importantly, resource utilisation and feeding mechanism complementarities and synergies along this specialisation continuum can have positive effects on pest control (Tylianakis & preference over broad-spectrum chemicals is being encouraged by IPM researchers and practitioners (Gentz et al 2010;Umina et al 2015;Torres & Bueno 2018). Some studies have investigated the lethal, sub-lethal and transgenerational effects of selective pesticides on a range of beneficial species (Croft & Whalon 1982;Flexner et al 1986;Fountain & Medd 2015;Mills et al 2016;Siviter & Muth 2020;Wu et al 2022;Knapp et al 2023a;Overton et al 2023;McDougall et al in press). However, evidence on whether these chemicals can control targeted pests without precipitating adverse effects across a range of beneficials including those that are regionally and seasonally restricted remains scarce.…”