Imidacloprid Poisoning of Songbirds Following a Drench Application of Trees in a Residential Neighborhood in California, USA

Wildlife ecotoxicology of plant protection products: knowns and unknowns about the impacts of currently used pesticides on terrestrial vertebrate biodiversity

Agricultural practices are a major cause of the current loss of biodiversity. Among postwar agricultural intensification practices, the use of plant protection products (PPPs) might be one of the prominent drivers of the loss of wildlife diversity in agroecosystems. A collective scientific assessment was performed upon the request of the French Ministries responsible for the Environment, for Agriculture and for Research to review the impacts of PPPs on biodiversity and ecosystem services based on the scientific literature. While the effects of legacy banned PPPs on ecosystems and the underlying mechanisms are well documented, the impacts of current use pesticides (CUPs) on biodiversity have rarely been reviewed. Here, we provide an overview of the available knowledge related to the impacts of PPPs, including biopesticides, on terrestrial vertebrates (i.e. herptiles, birds including raptors, bats and small and large mammals). We focused essentially on CUPs and on endpoints at the subindividual, individual, population and community levels, which ultimately linked with effects on biodiversity. We address both direct toxic effects and indirect effects related to ecological processes and review the existing knowledge about wildlife exposure to PPPs. The effects of PPPs on ecological functions and ecosystem services are discussed, as are the aggravating or mitigating factors. Finally, a synthesis of knowns and unknowns is provided, and we identify priorities to fill gaps in knowledge and perspectives for research and wildlife conservation.

Impacts of neonicotinoids on biodiversity: a critical review

Neonicotinoids are the most widely used class of insecticides in the world, but they have raised numerous concerns regarding their effects on biodiversity. Thus, the objective of this work was to do a critical review of the contamination of the environment (soil, water, air, biota) by neonicotinoids (acetamiprid, clothianidin, imidacloprid, thiacloprid, thiamethoxam) and of their impacts on terrestrial and aquatic biodiversity. Neonicotinoids are very frequently detected in soils and in freshwater, and they are also found in the air. They have only been recently monitored in coastal and marine environments, but some studies already reported the presence of imidacloprid and thiamethoxam in transitional or semi-enclosed ecosystems (lagoons, bays, and estuaries). The contamination of the environment leads to the exposure and to the contamination of non-target organisms and to negative effects on biodiversity. Direct impacts of neonicotinoids are mainly reported on terrestrial invertebrates (e.g., pollinators, natural enemies, earthworms) and vertebrates (e.g., birds) and on aquatic invertebrates (e.g., arthropods). Impacts on aquatic vertebrate populations and communities, as well as on microorganisms, are less documented. In addition to their toxicity to directly exposed organisms, neonicotinoid induce indirect effects via trophic cascades as demonstrated in several species (terrestrial and aquatic invertebrates). However, more data are needed to reach firmer conclusions and to get a clearer picture of such indirect effects. Finally, we identified specific knowledge gaps that need to be filled to better understand the effects of neonicotinoids on terrestrial, freshwater, and marine organisms, as well as on ecosystem services associated with these biotas.

Multiple Aspects of the Fight against the Red Palm Weevil in an Urban Area: Study Case, San Benedetto del Tronto (Central Italy)

The fight against alien invasive insect pests of plants in the urban environment often affects varied sectors of the economy, landscape gardening, public health, and ecology. This paper focuses on the evolution of the red palm weevil in San Benedetto del Tronto, a coastal urban area in central Italy. We investigated the evolution of this insect pest of palm trees in the 2013-2020 period, considering both the effectiveness of the chemicals used and their potentially harmful effects. With a multidisciplinary approach, we carried out a spatio-temporal analysis of the extent and mode of pest spread over time using historical aerial photos, freely available remote sensing images, and field surveys integrated in a GIS environment. We also assessed the toxicity risk associated with the chemicals used to protect the palms from the red weevil. The fight against this weevil is now concentrated in specific areas such as parks, roads, villas, hotels, farmhouses, and nurseries. The preventive chemical treatments applied are very effective in preserving the palms, but they show a toxic potential for all organisms. We discuss current local management of this pest, focusing on several aspects involved in the fight against this beetle in an urban area.

Insights into the ubiquity, persistence and microbial intervention of imidacloprid

Imidacloprid, a neonicotinoid pesticide, is employed to increase crop productivity. Meanwhile, its indiscriminate application severely affects the non-target organisms and the environment. As an eco-friendly and economically workable option, the microbial intervention has garnered much attention. This review concisely outlines the toxicity, long-term environmental repercussions, degradation kinetics, biochemical pathways, and interplay of genes implicated in imidacloprid remediation. The studies have highlighted imidacloprid residue persistence in the environment for up to 3000 days. In view of high persistence, effective intervention is highly required. Bacteria-mediated degradation has been established as a viable approach with Bacillus spp. being among the most efficient at 30 ℃ and pH 7. Further, a comparative metagenomic investigation reveals dominant neonicotinoid degradation genes in agriculture compared to forest soils with distinctive microbial communities. Functional metabolism of carbohydrates, amino acids, fatty acids, and lipids demonstrated a significantly superior relative abundance in forest soil, implying its quality and fertility. The CPM, CYP4C71v2, CYP4C72, and CYP6AY3v2 genes that synthesize cyt p450 monooxygenase enzyme play a leading role in imidacloprid degradation. In the future, a systems biology approach incorporating integrated kinetics should be utilized to come up with innovative strategies for moderating the adverse effects of imidacloprid on the environment.

High population prevalence of neonicotinoids in sharp-tailed grouse and greater prairie-chickens across an agricultural gradient during spring and fall

Neonicotinoids have been detected in many species of wild birds; however, few studies have quantified population-level exposure. We examined population-level exposure to 7 neonicotinoids in 2 species that use agricultural areas, sharp-tailed grouse (Tympanuchus phasianellus) and greater prairie-chickens (T. cupido). We sampled fecal pellets at leks in spring and collected livers from hunter-harvested birds in fall along an agricultural gradient throughout their respective ranges in Minnesota, USA. Most sharp-tailed grouse (93 %) and prairie-chicken (80 %) fecal pellets and livers (90 % and 76 %, respectively) had detectable concentrations of ≥1 neonicotinoid, with imidacloprid (IMI) and clothianidin (CLO) most commonly detected. Spring detections of IMI in both species increased with the proportion of a 2-km buffer in cultivation surrounding sampling locations and varied by year. A similar relationship with cultivation was not supported for CLO, which may reflect differences in the availability of seed types treated with IMI and CLO on the soil surface after planting. However, we also detected IMI and CLO from birds sampled in areas of low cultivation. Sharp-tailed grouse and prairie-chickens may select crop fields preferentially to forage, and thus have a higher risk of exposure than would be expected based only on the amount of cultivation. Year was important in models of IMI and CLO in both species and seasons, which likely reflects differences in planting and in the availability of natural foods among years. In contrast, the proportion of surrounding area in cultivation was not supported in models of fall neonicotinoid detections. Fewer crops are planted in the fall in Minnesota and grouse may be exposed through routes other than treated seeds. High detections, even in areas with little cultivation and during seasons with little planting, likely reflect prairie grouse selection of cultivated fields for food, but may also indicate that exposure risk extends beyond sites of application.

Avoidance of neonicotinoid-treated seeds and cotyledons by captive eared doves (Zenaida auriculata, Columbidae)

Farmland birds can be exposed to neonicotinoids through the ingestion of treated unburied seeds and cotyledons. The aim of this study was to evaluate the avoidance of sorghum with imidacloprid, clothianidin or thiamethoxam, soybean with imidacloprid, and soybean cotyledons with imidacloprid or thiamethoxam on eared doves (Zenaida auriculata). Doves were fed with test food (untreated and neonicotinoid-treated sorghum, soybean or soybean cotyledons) and maintenance food (seed mix) for 3-5 days to study the repellency (primary repellency and conditioned aversion) and anorexia caused by neonicotinoid-treated food, followed by a 7-day period on maintenance food to study the persistence of the anorexic effect after neonicotinoid exposure. Immediately afterward, the same doves were exposed to treated test food during a second period of 3-5 days to study the potential reinforcement of food avoidance. Finally, doves were fed with untreated test food to test the capacity of the pesticide to induce conditioned food aversion against untreated food in subsequent encounters. Intoxication signs and differences of body weight were determined. With sorghum, the three neonicotinoids produced a decrease in the consumption of treated seeds by >97% compared to control birds. However, this was not enough to prevent the death of 3/8 and 1/8 of the doves exposed to imidacloprid and clothianidin, respectively. Anorexia was clearly observed with neonicotinoid-treated sorghum. The birds did not avoid the untreated sorghum after exposure to the treated sorghum, indicating that avoidance is not generalized to the type of food without an associated sensory cue. The results obtained with soybean seeds and cotyledons were less conclusive because captive doves hardly consumed these foods, even without neonicotinoid treatment. The avoidance of sorghum seeds treated with neonicotinoids was insufficient to prevent poisoning and death of eared doves.

Effects of imidacloprid on viability and increase of reactive oxygen and nitrogen species in HepG2 cell line

Imidacloprid (IMD) is a neonicotinoid insecticide used in large quantities worldwide in both veterinary and agronomic applications. Several studies have shown adverse effects of IMD on non-target organisms, with the liver being identified as the main affected organ. This study aimed to evaluate the effects of IMD on human hepatoblastoma (HepG2) cells. HepG2 were exposed to IMD (0.25-2.0 mM) for 24 and 48 h. IMD treatment resulted in cytotoxicity in the HepG2, inhibiting cell proliferation in a dose- and time-dependent manner, starting at concentrations of 0.5 mM (24 h) and 0.25 mM (48 h), and reducing cell viability from 0.5 mM onwards (24 and 48 h). IMD significantly decreased the mitochondrial membrane potential at both time points investigated (2.0 mM), and also induced damage to the cell membrane, demonstrated by significant dose and time-dependent increases in lactate dehydrogenase (LDH) release from concentrations of 1.0 mM (24 h) and 0.5 mM (48 h) upwards. IMD treatment also increased the production of reactive oxygen and nitrogen species (ROS/RNS) at rates above 50% following 0.5 mM (24 h) or 0.25 mM (48 h) concentrations, and caused a significant decrease in reduced/oxidized glutathione ratio (GSH/GSSG), indicating oxidative stress. Furthermore, the antioxidant dithiothreitol, which reacts with ROS/RNS and acts as a thiol reducing agent, inhibited the cytotoxic effect of IMD. In addition, the metabolite IMD-olefin was more toxic than IMD. Our results indicate that IMD induces cytotoxicity in HepG2 cells and that this effect may be associated with an increase in the generation of ROS/RNS.

Agricultural pesticides and ectoparasites: potential combined effects on the physiology of a declining aerial insectivore

Agricultural pesticides usage has been increasing globally. These compounds have been developed to disrupt pest species physiology, but because their specificity is limited, they can also have adverse effects on non-target organisms. Recent studies have shown that the damaging toxicological effects of pesticides can be amplified in stressful environments. However, few studies have documented these effects in natural settings where organisms are simultaneously exposed to pesticides and to other environmental stressors such as parasites. In this study, we assessed both pesticide and ectoparasite effects on the physiology of a free-ranging bird. We measured physiological markers including haematocrit, bacteria-killing ability (BKA) and leucocyte counts, as well as exposure to haematophagous Protocalliphora larvae, in tree swallow nestlings (Tachycineta bicolor), a declining aerial insectivore, in southern Québec, Canada, for over 3 years. We found that combined exposure to pesticides and Protocalliphora larvae was negatively related to haematocrit, suggesting possible synergistic effects. However, we found no such relationships with BKA and leucocyte counts, highlighting the complexity of physiological responses to multiple stressors in natural settings. Populations of several aerial insectivores are declining, and although sublethal pesticide effects on physiology are suspected, our results suggest that exposure to other factors, such as parasitism, should also be considered to fully assess these effects, especially because pesticides are increasingly present in the environment.

Imidacloprid seed coating poses a risk of acute toxicity to small farmland birds: A weight-of-evidence analysis using data from the grayish baywing Agelaioides badius

The aim of this study was to estimate the risk posed by imidacloprid (IMI) seed coating to passerine birds of the Pampa Region of Argentina using data specifically generated with the grayish baywing (Agelaioides badius). Median lethal dose (LD₅₀) of the IMI-based formulation tested was 57.11 mg IMI/kg body weight (bw), with intoxication signs starting from 20.6 mg IMI/kg bw. The feed intake rate (FIR) was estimated experimentally as 4.895 g/day per bird, representing 12.43% of bw. It was calculated that the ingestion of 7-10% of the FIR as treated seeds would be enough to achieve the LD₅₀ for sorghum, corn, sunflower, and alfalfa, whereas consumption of 31 and 54% of FIR was necessary for oat and wheat, respectively. Based on spill data values available in the literature, it was calculated that, for most crops, a baywing would have to forage an area of field corresponding to less than 60 m² to obtain the number of seeds required to reach the LD₅₀. It was also shown that this number of seeds is coherent with the amount of seeds ingested in a bout. In a pilot study, all grayish baywings fed with millet seeds treated with 3 g IMI/kg died within three to five days of exposure. In Tier I risk assessment, the trigger value was achieved for all crops except soybean and a weight-of-evidence risk assessment was performed. All lines of evidence examined are consistent with the view that grayish baywings, and probably other small farmland birds, are exposed to a risk of acute toxicity and mortality under both worst-case and mixed-ration exposure scenarios. The possible impacts on bird species calls for an urgent reconsideration of IMI seed coating practices currently approved in the Pampa Region of Argentina and the various parts of the world where this practice is still in use.

Characterizing imidacloprid and metabolites in songbird blood with applications for diagnosing field exposures

Neonicotinoids are the most widely used insecticides globally, but their rapid metabolism in vertebrates makes diagnosing wildlife exposure challenging. More detailed information on the pattern of imidacloprid metabolites over time could be used to better approximate the timing and level of exposure. Here, we applied recently developed sensitive analytical methods to measure imidacloprid (IMI) parent compound along with an expanded suite of metabolites (5-OH-IMI, IMI-olefin, desnitro-IMI, IMI-urea, 6-chloronicotinic acid, 5-AMCP, 6-OH nicotinic acid) and six other neonicotinoids in adult red-winged blackbirds (Agelaius phoeniceus) that were experimentally exposed to one of two field-realistic concentrations of imidacloprid (0.8 or 6.9 mg/kg bw). We measured concentrations in small (25 μL) plasma samples collected pre-exposure and at 1-, 6-, 24- and 48-h post-exposure. Imidacloprid was rapidly absorbed and metabolized within 48 h at both doses, with the largest decrease within 6 h post-exposure. The average proportion of parent IMI decreased from 68% of total detectable residues at 1-h to 34% at 6-h post-exposure. Two primary metabolites in blood were 5-OH-IMI and IMI-olefin, and 5-OH-IMI was the most persistent marker of exposure at 48-h. Desnitro-IMI was consistently detected following very recent (≤ 1-h) IMI exposure, and a higher ratio of parent IMI to metabolites also indicated recent exposure. Other metabolites were only detected in the higher dose group, and could be used as indicators of exposure to higher IMI concentrations. This sensitive analytical method and the observed metabolite patterns could be used to inform a growing body of field studies linking neonicotinoid exposure and effects in free-living birds.

Wildlife consumption of neonicotinoid-treated seeds at simulated seed spills

The most likely route of exposure to high concentrations of neonicotinoids capable of producing lethal or sublethal effects in birds and mammals is consumption of treated seeds. We placed trail cameras at simulated seed spills to document wildlife consuming treated seeds during the spring planting season. We simulated 4 types of spills, corn treated with 2 concentrations of clothiandin (0.50 or 0.25 mg/seed), corn treated with thiamethoxam (0.25 mg/seed), and soybean treated with imidacloprid (0.15 mg/seed). We documented 16 species of birds and 14 species of mammals eating neonicotinoid-treated seeds at spills. Of these, we quantified consumption of treated seeds by 12 species of birds and 13 species of mammals. Birds and mammals did not consume enough seeds to exceed published LD50s in related taxa, but most species did consume enough seeds to reach or exceed thresholds for sublethal effects based on currently available studies. Birds and mammals did not increase the amount of seeds consumed over time, as would be expected if responsive to the concentration of neonicotinoids on seeds, but more birds and mammals consumed seeds over time, as a proportion of the number at spills each day. More birds also consumed seeds after a soaking rain event, which likely reduced the amount of treatment on the seeds. Importantly, wildlife are consuming seeds while neonicotinoids are still concentrated on seeds. Our findings indicate that previously held assumptions about the safety of neonicotinoid seed treatments for vertebrate wildlife need to be revisited.

Determination of neonicotinoids and butenolide residues in avian and insect pollinators and their ambient environment in Western Canada (2017, 2018)

To examine the spatial, and temporal variation and potential sources of pesticide concentrations, primarily neonicotinoid insecticides, in hummingbirds in western Canada, we sampled their cloacal fluid from sites in British Columbia and Saskatchewan, Canada in 2017-2018. At a sub-sample of those sites, we also measured pesticides in honey bee (Apis mellifera) nectar, water, and sediment. We collected cloacal fluid from 5 species of hummingbirds (n = 26 sites) in British Columbia (BC) and Saskatchewan, Canada, and nectar from honey bee hives (n = 4 sites), water and sediment (n = 18 sites) in the Fraser Valley, BC. Among those, multiple types of samples were collected at 6 sites. We report the first measurement of flupyradifurone, a relatively new butenolide insecticide, in wildlife which was detected at 4.58 ng/mL in hummingbird cloacal fluid and 2.18 ng/g in honey bee nectar. We also detected three other neonicotinoids (imidacloprid, clothianidin, acetamiprid) and one metabolite desnitro-imidacloprid, and MGK264, a pesticide synergist, in our samples. Among 49 samples of cloacal fluid from rufous (Selasphorus rufus), Anna's (Calypte anna), calliope (Selasphorus calliope) black-chinned (Archilocus alexandri) and ruby-throated hummingbirds (Archilocus colubris), 26.5% (n = 13) contained neonicotinoids. Maximum pesticide concentrations in hummingbirds, water and sediment were found in samples collected in the Fraser Valley, BC within 0.5 km of conventionally sprayed blueberry fields (CSBF) but highest levels in honey bee nectar were detected at a site 1.5 km from a CSBF. Imidacloprid in honey bee nectar at one site exceeded concentrations (>1 ng/g) that can sublethally affect worker bee foraging efficiency. In water, imidacloprid concentrations at another site exceeded Canadian guidelines (230 ng/mL) for the protection of aquatic invertebrates.

Neonicotinoid-containing insecticide disruption of growth, locomotion, and fertility in Caenorhabditis elegans

Neonicotinoids, a class of insecticides structurally similar to nicotine that target biting and sucking insects, are the most widely used insecticides today, in part due to their supposed low toxicity in other organisms. However, a growing body of research has found that even low doses of neonicotinoids can induce unexpected negative effects on the physiology and survival of a wide range of non-target organisms. Importantly, no work has been done on the commercial formulations of pesticides that include imidacloprid as the active ingredient, but that also contain many other components. The present study examines the sublethal effects of "Tree and Shrub"™ ("T+S"), a commercial insecticide containing the neonicotinoid imidacloprid as its active ingredient, on Caenorhabditis elegans. We discovered that "T+S" significantly stunted the overall growth in wildtype nematodes, an effect that was exacerbated by concurrent exposure to heat stress. "T+S" also negatively impacted fecundity as measured by increased germline apoptosis, a decrease in egg-laying, and fewer viable offspring. Lastly, exposure to "T+S" resulted in degenerative changes in nicotinic cholinergic neurons in wildtype nematodes. As a whole, these findings demonstrate widespread toxic effects of neonicotinoids to critical functions in nematodes.

Sublethal and Lethal Methods to Detect Recent Imidacloprid Exposure in Birds with Application to Field Studies

We used domestic chickens (Gallus gallus domesticus) as a model for granivorous birds to identify methods to detect recent imidacloprid exposure in wild birds. We conducted dosing experiments of 1, 5, 10, and 20% of a reported median lethal dose for domestic chickens using repeated daily exposures over 7 d, at dosages equating to 1.04, 5.2, 10.4, and 20.8 mg/kg/d. We examined the parent compound and metabolites in serial collections of feces and blood during exposures and for 15 d after exposures. We also collected liver, kidney, brain, muscle, and spleen at the experiment end. Mean concentrations of parent compound at 15 d postexposure were highest in the feces and brain, followed by the liver, muscle, spleen, and kidney; but mean concentrations of metabolites 5-OH-imidacloprid and imidacloprid-olefin were highest in feces; then liver, spleen, muscle, and kidney; and then brain. Imidacloprid was rapidly cleared from blood, with only one individual in any dose group having detectable concentrations after 48 h. In contrast, fecal pellets had the highest frequency of imidacloprid detection after 15 d. Concentrations of metabolites were higher than those of the parent compound at all sampling times examined but provided no information about time since exposure. Feces may provide a reliable nonlethal method for detection of recent imidacloprid exposure in wild birds. Additional work is needed to disentangle exposure dose concentration and time since exposure in field-collected samples. Environ Toxicol Chem 2020;39:1355-1366. © 2020 SETAC.