Insecticide residues in Australian plague locusts (Chortoicetes terminifera walker) after ultra‐low volume aerial application of the organophosphorus insecticide fenitrothion

Abstract

The need for locust control throughout eastern Australia during spring 2010 provided an opportunity to quantify residues of the organophosphorus insecticide fenitrothion on nymphs of the Australian plague locust, Chortoicetes terminifera Walker. Residues were collected across the different physiological states--live, dead, and debilitated (characterized by ease of capture, erratic hopping, and the inability to remain upright)--of locust nymphs observed following exposure to fenitrothion. The time course of residue depletion for 72 h after spraying was quantified, and residue-per-unit dose values in the present study were compared with previous research. Fenitrothion residue-per-unit dose values ranged from 0.2 µg/g to 31.2 µg/g (mean ± standard error [SE] = 6.3 ± 1.3 µg/g) in live C. terminifera nymps, from 0.5 µg/g to 25.5 µg/g (7.8 ± 1.3 µg/g) in debilitated nymphs, and from 2.3 µg/g to 39.8 µg/g (16.5 ± 2.8 µg/g) in dead nymphs. Residues of the oxidative derivative of fenitrothion, fenitrooxon, were generally below the limit of quantitation for the analysis (0.02 µg/g), with 2 exceptions--1 live and 1 debilitated sample returned residues at the limit of quantitation. The results of the present study suggest that sampling of acridids for risk assessment should include mimicking predatory behavior and be over a longer time course (preferably 3-24 h postspray) than sampling of vegetation (typically 1-2 h postspray) and that current regulatory frameworks may underestimate the risk of pesticides applied for locust or grasshopper control.

Sublethal pesticide exposure influences behaviour, but not condition in a widespread Australian lizard

“…As fipronil was a powder it was first dissolved in a minimum amount of acetone (acetone solubility = 54.6 g/100 ml) ( Tingle et al, 2003 ; Kitulagodage et al, 2011a ), before suspension in corn oil. Pesticide dose was calculated based on previous literature and pilot data incorporating maximum feeding rates and pesticide residue levels found on natural prey and vegetation after locust control operations in Australia ( Szabo, 2005 ; Story et al, 2013 ), with the aim to administer an ecologically relevant dose. Mimicking the average diet of an adult lizard (70% vegetation and 30% insects) we applied this knowledge to known residue levels of both pesticides on vegetation and locusts.…”

“…Pesticides can be applied to large areas by aircraft spraying ultra-low volume formulations ( Story and Cox, 2001 ; Sinervo et al, 2010 ). In the arid zone of Australia, fenitrothion (O,O-dimethyl-O-(3-methyl-4-nitrophenol)-phosphorothioate, CAS 122-14-5) and fipronil (5-amino-3-cyano-1-(2,6-dichloro-4-trifluoromethylphenyl)-4-trifluoromethylsulfinyl pyrazole, CAS 120068-37-3) are applied aerially for locust control ( Story et al, 2013 ; Maute et al, 2017 ; APLC, 2020 ). Fenitrothion is a broad-spectrum organophosphate insecticide widely used in agricultural pest control ( Story et al, 2021 ).…”

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“…This implies that newly arriving (sub)adult locusts and locust hatchlings emerging in treated fields within that period may also become infected. This strongly contrasts with synthetic insecticides which rapidly decay on vegetation [40] and do not guarantee any longer lasting effect on newly arriving locusts or emerging nymphs, while causing ecotoxicological side-effects and potentially human health risks. The observed combination of significant increases in acridivorous bird numbers without having a negative impact on other locust predators, both diurnal and nocturnal, has the potential to further enhance the long-lasting effect of GM treatments, offering substantial additional advantages for selective locust control operations.…”

“…This means that newly arriving or surviving locusts hardly encounter natural enemies anymore, potentially leading to a secondary pest outbreak [6]. In addition, synthetic pesticide applications can also damage other ecosystem functions and insecticide residues may pose risks for the avian and even human food chain [40,41]. Many desert locust treatments are carried out in remote arid areas and side effects on birds and other beneficial organisms are rarely monitored [23] despite the existence of FAO recommendations [42].…”

“…Many desert locust treatments are carried out in remote arid areas and side effects on birds and other beneficial organisms are rarely monitored [23] despite the existence of FAO recommendations [42]. This will probably result in underestimates of the impacts of synthetic pesticides applied for locust or grasshopper control [40] in the longer term.…”