Effects of field-relevant concentrations of clothianidin on larval development of the butterfly Polyommatus icarus (Lepidoptera, Lycaenidae)

Arable field margins are often sown with wild flowers to encourage pollinators and other beneficial or desirable insects such as bees and butterflies. Concern has been raised that these margins may be contaminated with systemic pesticides such as neonicotinoids used on the adjacent crop, and that this may negatively impact on beneficial insects. The use of neonicotinoids has been linked to butterfly declines, and species such as the common blue butterfly (Polyommatus icarus) that feed upon legumes commonly sown in arable field margins, may be exposed to such toxins. Here, we demonstrate that the larval foodplants of P. icarus growing in an arable field margin adjacent to a wheat crop treated with the neonicotinoid clothianidin, not only contain the pesticide at concentrations comparable to and sometimes higher than those found in foliage of treated crops (range 0.2 to 48 ppb), but remain detectable at these levels for up to 21 months after sowing the crop. Overall, our study demonstrates that non-target herbivorous organisms in arable field margins are likely to be chronically exposed to neonicotinoids. Under laboratory conditions, exposure to clothianidin at 15ppb (a field-realistic dose) or above reduced larval growth for the first 9 days of the experiment. Although there was evidence of clothianidin inducing mortality in larvae, with highest survival in control groups, the dose-response relationship was unclear. Our study suggests that larvae of this butterfly exhibit some deleterious sublethal and sometimes lethal impacts of exposure to clothianidin, but many larvae survive to adulthood even when exposed to high doses

The effect of neonicotinoid pesticides on non-target organisms

There is widespread concern over the use of neonicotinoid pesticides in agro-ecosystems, and their effects on the wider environment. This is due in part to their high solubility in water which can lead to widespread contamination of non-target areas including standing surface water, soil, and non-target vegetation. The contribution of neonicotinoid exposure to the ongoing wild pollinator population declines has been the focus of considerable in-depth recent research, focused on the impacts on honeybees, bumblebees, and more recently on solitary bees. However, relatively little research has examined the impacts of exposure on other beneficial non-target organisms. This thesis investigates the impact of field-relevant concentrations of two neonicotinoids: thiamethoxam and clothianidin, on a range of non-model organisms. Model systems were developed for laboratory based experiments on three species: the hoverfly Eristalis tenax; the butterfly Polyommatus icarus; and the earth worm Lumbricus terrestris. A further semi-field experiment investigated the colonisation of contaminated microcosms by aquatic invertebrates. An additional review and analysis of UK time series data tested the relationship between agricultural change (including neonicotinoid usage) and changes in multi-species farmland bird populations. Principally, the results corroborate previous research on non-target organisms and neonicotinoid exposure, showing a negative effect on mortality, food consumption and growth across a range of organisms. Clothianidin decreased the survival of Lumbricus terrestris, exposed via treated soil. Field-realistic exposure also had a significant but temporary effect on food consumption. Sublethal – and sometimes lethal – impacts of clothianidin were also found on the larvae of Polyommatus icarus. Both clothianidin and thiamethoxam showed significant negative effects on Diptera and Ostracoda, with clear differences between the effects of the two chemicals. In contrast, the larval stage of the hoverfly Eristalis tenax was unaffected by field realistic doses of thiamethoxam, with no observed effects on survival or development, nor showed any latent effects on adult activity budgets resulting from exposure to lower concentrations. The re-analysis of the relationship between agricultural change and bird population changes confirmed that evolving agricultural practices continue to affect farmland birds; a moderately significant negative relationship was found between bird population change and neonicotinoid exposure risk. This thesis shows that neonicotinoids have a range of varying and unpredictable negative impacts on diverse invertebrate taxa; and demonstrates that it is possible to develop new model systems to test the effects of pesticides on often-overlooked taxa

Neonicotinoids thiamethoxam and clothianidin adversely affect the colonisation of invertebrate populations in aquatic microcosms

Surface waters are sometimes contaminated with neonicotinoids: a widespread, persistent, systemic class of insecticide with leaching potential. Previous ecotoxicological investigations of this chemical class in aquatic ecosystems have largely focused on the impacts of the neonicotinoid imidacloprid; few empirical, manipulative studies have investigated the effect on invertebrate abundances of two other neonicotinoids which are now more widely used: clothianidin and thiamethoxam. In this study, we employ a simple microcosm semi-field design, incorporating a one-off contamination event, to investigate the effect of these pesticides at field-realistic levels (ranging from 0 to 15 ppb) on invertebrate colonisation and survival in small ephemeral ponds. In line with previous research on neonicotinoid impacts on aquatic invertebrates, significant negative effects of both neonicotinoids were found. There were clear differences between the two chemicals, with thiamethoxam generally producing stronger negative effects than clothianidin. Populations of Chironomids (Diptera) and Ostracoda were negatively affected by both chemicals, while Culicidae appeared to be unaffected by clothianidin at the doses used. Our data demonstrate that field-realistic concentrations of neonicotinoids are likely to reduce populations of invertebrates found in ephemeral ponds, which may have knock on effects up the food chain. We highlight the importance of developing pesticide monitoring schemes for European surface waters

The effect of neonicotinoid pesticides on non-target organisms

There is widespread concern over the use of neonicotinoid pesticides in agro-ecosystems, and their effects on the wider environment. This is due in part to their high solubility in water which can lead to widespread contamination of non-target areas including standing surface water, soil, and non-target vegetation. The contribution of neonicotinoid exposure to the ongoing wild pollinator population declines has been the focus of considerable in-depth recent research, focused on the impacts on honeybees, bumblebees, and more recently on solitary bees. However, relatively little research has examined the impacts of exposure on other beneficial non-target organisms. This thesis investigates the impact of field-relevant concentrations of two neonicotinoids: thiamethoxam and clothianidin, on a range of non-model organisms. Model systems were developed for laboratory based experiments on three species: the hoverfly Eristalis tenax; the butterfly Polyommatus icarus; and the earth worm Lumbricus terrestris. A further semi-field experiment investigated the colonisation of contaminated microcosms by aquatic invertebrates. An additional review and analysis of UK time series data tested the relationship between agricultural change (including neonicotinoid usage) and changes in multi-species farmland bird populations. Principally, the results corroborate previous research on non-target organisms and neonicotinoid exposure, showing a negative effect on mortality, food consumption and growth across a range of organisms. Clothianidin decreased the survival of Lumbricus terrestris, exposed via treated soil. Field-realistic exposure also had a significant but temporary effect on food consumption. Sublethal – and sometimes lethal – impacts of clothianidin were also found on the larvae of Polyommatus icarus. Both clothianidin and thiamethoxam showed significant negative effects on Diptera and Ostracoda, with clear differences between the effects of the two chemicals. In contrast, the larval stage of the hoverfly Eristalis tenax was unaffected by field realistic doses of thiamethoxam, with no observed effects on survival or development, nor showed any latent effects on adult activity budgets resulting from exposure to lower concentrations. The re-analysis of the relationship between agricultural change and bird population changes confirmed that evolving agricultural practices continue to affect farmland birds; a moderately significant negative relationship was found between bird population change and neonicotinoid exposure risk. This thesis shows that neonicotinoids have a range of varying and unpredictable negative impacts on diverse invertebrate taxa; and demonstrates that it is possible to develop new model systems to test the effects of pesticides on often-overlooked taxa

Effects of field-relevant concentrations of clothianidin on larval development of the butterfly Polyommatus icarus (Lepidoptera, Lycaenidae)

Arable field margins are often sown with wild flowers to encourage pollinators and other beneficial or desirable insects such as bees and butterflies. Concern has been raised that these margins may be contaminated with systemic pesticides such as neonicotinoids used on the adjacent crop, and that this may negatively impact on beneficial insects. The use of neonicotinoids has been linked to butterfly declines, and species such as the common blue butterfly (Polyommatus icarus) that feed upon legumes commonly sown in arable field margins, may be exposed to such toxins. Here, we demonstrate that the larval foodplants of P. icarus growing in an arable field margin adjacent to a wheat crop treated with the neonicotinoid clothianidin, not only contain the pesticide at concentrations comparable to and sometimes higher than those found in foliage of treated crops (range 0.2 to 48 ppb), but remain detectable at these levels for up to 21 months after sowing the crop. Overall, our study demonstrates that non-target herbivorous organisms in arable field margins are likely to be chronically exposed to neonicotinoids. Under laboratory conditions, exposure to clothianidin at 15ppb (a field-realistic dose) or above reduced larval growth for the first 9 days of the experiment. Although there was evidence of clothianidin inducing mortality in larvae, with highest survival in control groups, the dose-response relationship was unclear. Our study suggests that larvae of this butterfly exhibit some deleterious sublethal and sometimes lethal impacts of exposure to clothianidin, but many larvae survive to adulthood even when exposed to high doses

Neonicotinoids thiamethoxam and clothianidin adversely affect the colonisation of invertebrate populations in aquatic microcosms

Surface waters are sometimes contaminated with neonicotinoids: a widespread, persistent, systemic class of insecticide with leaching potential. Previous ecotoxicological investigations of this chemical class in aquatic ecosystems have largely focused on the impacts of the neonicotinoid imidacloprid; few empirical, manipulative studies have investigated the effect on invertebrate abundances of two other neonicotinoids which are now more widely used: clothianidin and thiamethoxam. In this study, we employ a simple microcosm semi-field design, incorporating a one-off contamination event, to investigate the effect of these pesticides at field-realistic levels (ranging from 0 to 15 ppb) on invertebrate colonisation and survival in small ephemeral ponds. In line with previous research on neonicotinoid impacts on aquatic invertebrates, significant negative effects of both neonicotinoids were found. There were clear differences between the two chemicals, with thiamethoxam generally producing stronger negative effects than clothianidin. Populations of Chironomids (Diptera) and Ostracoda were negatively affected by both chemicals, while Culicidae appeared to be unaffected by clothianidin at the doses used. Our data demonstrate that field-realistic concentrations of neonicotinoids are likely to reduce populations of invertebrates found in ephemeral ponds, which may have knock on effects up the food chain. We highlight the importance of developing pesticide monitoring schemes for European surface waters

Data for research article "Neonicotinoids Thiamethoxam and Clothianidin Adversely Affect the Colonisation of Freshwater Microcosms"

Raw data from counting the colonisation of invertebrate populations in aquatic microcosms. Each column is total number of that invertebrate in that microscosm.Effects of both thiamethoxam and clothianidin were investigated.Abstract from articleSurface waters are sometimes contaminated with neonicotinoids: a widespread, persistent, systemic class of insecticide with leaching potential. Previous ecotoxicological investigations of this chemical class in aquatic ecosystems have largely focused on the impacts of the neonicotinoid imidacloprid; few empirical, manipulative studies have investigated the effect on invertebrate abundances of two other neonicotinoids which are now more widely used: clothianidin and thiamethoxam. In this study, we employ a simple microcosm semi-field design, incorporating a one-off contamination event, to investigate the effect of these pesticides at field-realistic levels (ranging from 0 to 15 ppb) on invertebrate colonisation and survival in small ephemeral ponds. In line with previous research on neonicotinoid impacts on aquatic invertebrates, significant negative effects of both neonicotinoids were found. There were clear differences between the two chemicals, with thiamethoxam generally producing stronger negative effects than clothianidin. Populations of Chironomids (Diptera) and Ostracoda were negatively affected by both chemicals, while Culicidae appeared to be unaffected by clothianidin at the doses used. Our data demonstrate that field-realistic concentrations of neonicotinoids are likely to reduce populations of invertebrates found in ephemeral ponds, which may have knock on effects up the the food chain.We highlight the importance of developing pesticide monitoring schemes for European surface waters.</div

Effects of chronic exposure to clothianidin on the earthworm Lumbricus terrestris

Although neonicotinoids are targeted at insects, their predominant use as a seed dressing and their long persistence in soils mean that non-target soil organisms such as earthworms are likely to be chronically exposed to them. Chronic exposure may pose risks that are not evaluated in most toxicity tests. We experimentally tested the effect of field-realistic concentrations of a commonly used neonicotinoid, clothianidin, on mortality, weight gain, and food consumption to assess the impacts of chronic exposure over four months on fitness of L. terrestris individuals. We undertook three separate experiments, each with different exposure routes: treated soil only (experiment A), treated food and soil combined (experiment B) and treated food only (experiment C). Mortality was negatively affected by exposure from treated soil only with greatest mortality observed in the groups exposed to the two highest concentrations (20 ppb and 100 ppb), but no clear effect on mortality was found in the other two experiments. When clothianidin was present in the food, an anti-feedant effect was present in months one and two which subsequently disappeared; if this occurs in the field, it could result in reduced rates of decomposition of treated crop foliage. We found no significant effects of any treatment on worm body mass. We cannot rule out stronger adverse effects if worms come into close proximity to treated seeds, or if other aspects of fitness were examined. Overall, our data suggest that field-realistic exposure to clothianidin has a significant but temporary effect on food consumption and can have weak but significant impacts on mortality of L. terrestris

Effects of chronic exposure to thiamethoxam on larvae of the hoverfly Eristalis tenax (Diptera, Syrphidae)

There is widespread concern over the use of neonicotinoid pesticides in the agro-ecosystem, due in part to their high water solubility which can lead to widespread contamination of non-target areas including standing surface water. Most studies investigating the negative fitness consequences of neonicotinoids have focused on bees, with little research on the impact on other non-target insects. Here we examined the effect of exposure on the aquatic larval stages of the hoverfly Eristalis tenax L. (Diptera: Syrphidae) to a range of concentrations (control, 5, 15, 50, 100 and 500 ppb) of the neonicotinoid thiamethoxam; no published studies have thus far examined the effects of neonicotinoids on hoverflies. Survival was significantly lower when exposed to 500 ppb thiamethoxam, but this concentration exceeds that likely to be found in the field. We observed no effect on survival, development or any latent effects on adult activity budgets resulting from exposure to lower concentrations (up to 100 ppb). Our results suggest that E. tenax exposed as larvae to thiamethoxam are unlikely to be negatively impacted by this neonicotinoid under field conditions

Potential acetylcholine-based communication in honeybee haemocytes and its modulation by a neonicotinoid insecticide

There is growing concern that some managed and wild insect pollinator populations are in decline, potentially threatening biodiversity and sustainable food production on a global scale. In recent years, there has been increasing evidence that sub-lethal exposure to neurotoxic, neonicotinoid pesticides can negatively affect pollinator immunocompetence and could amplify the effects of diseases, likely contributing to pollinator declines. However, a direct pathway connecting neonicotinoids and immune functions remains elusive. In this study we show that haemocytes and non-neural tissues of the honeybee Apis mellifera express the building blocks of the nicotinic acetylcholine receptors that are the target of neonicotinoids. In addition, we demonstrate that the haemocytes, which form the cellular arm of the innate immune system, actively express choline acetyltransferase, a key enzyme necessary to synthesize acetylcholine. In a last step, we show that the expression of this key enzyme is affected by field-realistic doses of clothianidin, a widely used neonicotinoid. These results support a potential mechanistic framework to explain the effects of sub-lethal doses of neonicotinoids on the immune function of pollinators