Department of Entomology and Plant Pathology, Oklahoma State University, Stillwater, OK, 74078, USA.
U.S. Geological Survey, California Water Science Center, Sacramento, CA, 95819, USA.
Sci Rep. 2023 May 26;13(1):8537. doi: 10.1038/s41598-023-35262-w.
Dung beetles (Coleoptera: Scarabaeinae) frequently traverse agricultural matrices in search of ephemeral dung resources and spend extended periods of time burrowing in soil. Neonicotinoids are among the most heavily applied and widely detected insecticides used in conventional agriculture with formulated products designed for row crop and livestock pest suppression. Here, we determined the comparative toxicity of two neonicotinoids (imidacloprid and thiamethoxam) on dung beetles, Canthon spp., under two exposure profiles: direct topical application (acute) and sustained contact with treated-soil (chronic). Imidacloprid was significantly more toxic than thiamethoxam under each exposure scenario. Topical application LD50 values (95% CI) for imidacloprid and thiamethoxam were 19.1 (14.5-25.3) and 378.9 (200.3-716.5) ng/beetle, respectively. After the 10-day soil exposure, the measured percent mortality in the 3 and 9 µg/kg nominal imidacloprid treatments was 35 ± 7% and 39 ± 6%, respectively. Observed mortality in the 9 µg/kg imidacloprid treatment was significantly greater than the control (p = 0.04); however, the 3 µg/kg imidacloprid dose response may be biologically relevant (p = 0.07). Thiamethoxam treatments had similar mortality as the controls (p > 0.8). Environmentally relevant concentrations of imidacloprid measured in airborne particulate matter and non-target soils pose a potential risk to coprophagous scarabs.
蜣螂（鞘翅目：金龟子科）经常在农业基质中穿梭，寻找短暂的粪便资源，并在土壤中长时间挖掘。新烟碱类杀虫剂是在常规农业中应用最广泛、检测最广泛的杀虫剂之一，其配制产品用于作物和牲畜害虫防治。在这里，我们确定了两种新烟碱类杀虫剂（吡虫啉和噻虫嗪）对蜣螂（Canthon spp.）的比较毒性，暴露情况有两种：直接局部应用（急性）和持续接触处理过的土壤（慢性）。在每种暴露情况下，吡虫啉的毒性都明显大于噻虫嗪。吡虫啉和噻虫嗪的经皮 LD50 值（95%置信区间）分别为 19.1（14.5-25.3）和 378.9（200.3-716.5）ng/只蜣螂。在 10 天的土壤暴露后，3 和 9 µg/kg 名义吡虫啉处理的死亡率分别为 35±7%和 39±6%。9 µg/kg 吡虫啉处理的死亡率明显高于对照（p=0.04）；然而，3 µg/kg 吡虫啉剂量的反应可能具有生物学意义（p=0.07）。噻虫嗪处理的死亡率与对照相似（p>0.8）。空气中的颗粒物和非靶标土壤中检测到的环境相关浓度的吡虫啉对食粪金龟子构成潜在风险。
