Reproductive sublethal effects of macrocyclic lactones and synthetic pyrethroids on the dung beetle Onthophagus similis

Abstract

Dung-colonizing beetles provide a range of ecosystem services in farmland pasture systems. However, such beetles are declining in Northern temperate regions. This may, in part, be due to the widespread use of macrocyclic lactones (MLs) and synthetic pyrethroids (SPs) in livestock farming. These chemicals are used to control pests and parasites of cattle; the residues of which are excreted in dung at concentrations toxic to insects. While the lethal effects of such residues are well known, sublethal effects are less understood. Any effects, however, may have important consequences for beetle populations, particularly if they affect reproduction. To investigate, the impact of ML and SP exposure on the reproductive output of Onthophagus similis (Scriba), a Northern temperate dung beetle species, was examined. In laboratory trials, field-collected adult O. similis exposed to the ML ivermectin at 1 ppm (wet weight) over a period of 3 weeks had smaller oocytes (p = 0.016), smaller fat bodies and reduced motility compared to the control. In a farm-level investigation, cattle dung-baited pitfall trapping was undertaken on 23 beef cattle farms in SW England, which either used MLs (n = 9), SPs (n = 7) or neither chemical (n = 7). On farms that used no MLs or SPs, 24.2% of females caught were gravid. However, on farms that used MLs no gravid females were caught, and only 1% of the beetles caught on farms using SPs were gravid (p < 0.001). The association between ML and SP use and impaired reproductive output suggests that the use of such chemicals is likely to be ecologically damaging.

First report of eprinomectin-resistant isolates ofHaemonchus contortusin 5 dairy sheep farms from thePyrénées Atlantiques départementin France

“…The significant difference between mean concentrations of EPN in SC and T groups is observed although the dose rate for the topical solution is 5 times higher than for the injection solution (1 mg kg −1 of LBW for the topical solution and 0.2 mg kg −1 LBW for the injection solution). Given the impact of ML on non-target species such as dung beetles, elimination of the molecule, through direct contact or by the fecal matters, could have an impact on pasture quality (Sands and Wall, 2018 ; Verdú et al ., 2018 ; Weaving et al ., 2020 ).…”

Environmental impacts of equine parasiticide treatment: The UK perspective

“…The impacts of veterinary parasiticide residues in dung on important decomposer insect communities such as dung beetles and flies are well studied (Finch et al., 2020; Floate et al., 2005; Junco et al., 2021). Even at sub‐lethal concentrations, macrocyclic lactones and other anthelmintics can have a variety of other effects on dung‐colonising insects, including loss of water balance, disruption of feeding and reduced fat accumulation, delayed ovarian development, decreased fecundity and impaired mating (Strong & Wall, 1994; Weaving et al., 2020).…”

“…One study in cattle demonstrated reduced reproductive performance of the dung beetle Onthophagus similis on farms that use synthetic pyrethroids compared to those that do not (Weaving et al., 2020). Pyrethrins have very limited toxicity to birds and earthworms but are highly toxic to bees, fish and aquatic invertebrates.…”

Laboratory Determination of Particulate‐Matter–Bound Agrochemical Toxicity among Honeybees, Mason Bees, and Painted Lady Butterflies

“…Many research reports have detailed the lethal and sublethal toxic effects on insects of a variety of chemicals used in agriculture (Ansell et al, 2021; Bargar et al, 2020; Heller et al, 2020; Hladik et al, 2016; Ingram et al, 2015; Longing et al, 2020; Lv et al, 2023; Peterson et al, 2021a; Sandrock et al, 2014; Weaving et al, 2020; Zhao et al, 2020; Zhu et al, 2014). In terms of the present study, pyrethroids, neonicotinoids, and macrocyclic lactones are toxic to pollinators (see Li et al, 2023; Lv et al, 2023; Peterson et al, 2019; Peterson et al, 2021a).…”