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Concept: Imidacloprid effects on bee population


Growing evidence for global pollinator decline is causing concern for biodiversity conservation and ecosystem services maintenance. Neonicotinoid pesticides have been identified or suspected as a key factor responsible for this decline. We assessed the global exposure of pollinators to neonicotinoids by analyzing 198 honey samples from across the world. We found at least one of five tested compounds (acetamiprid, clothianidin, imidacloprid, thiacloprid, and thiamethoxam) in 75% of all samples, 45% of samples contained two or more of these compounds, and 10% contained four or five. Our results confirm the exposure of bees to neonicotinoids in their food throughout the world. The coexistence of neonicotinoids and other pesticides may increase harm to pollinators. However, the concentrations detected are below the maximum residue level authorized for human consumption (average ± standard error for positive samples: 1.8 ± 0.56 nanograms per gram).

Concepts: Biodiversity, Pollinator decline, Bee, Bumblebee, Pollinator, Insecticide, Neonicotinoid, Imidacloprid effects on bee population


Neonicotinoid seed treatments, typically clothianidin or thiamethoxam, are routinely applied to >80% of maize (corn) seed grown in North America where they are marketed as a targeted pesticide delivery system. Despite this widespread use, the amount of compound translocated into plant tissue from the initial seed treatment to provide protection has not been reported. Our two year field study compared concentrations of clothianidin seed treatments in maize to that of maize without neonicotinoid seed treatments and found neonicotinoids present in root tissues up to 34 days post planting. Plant-bound clothianidin concentrations followed an exponential decay pattern with initially high values followed by a rapid decrease within the first ~20 days post planting. A maximum of 1.34% of the initial seed treatment was successfully recovered from plant tissues in both study years and a maximum of 0.26% was recovered from root tissue. Our findings show neonicotinoid seed treatments may provide protection from some early season secondary maize pests. However, the proportion of the neonicotinoid seed treatment clothianidin translocated into plant tissues throughout the growing season is low overall and this observation may provide a mechanism to explain reports of inconsistent efficacy of this pest management approach and increasing detections of environmental neonicotinoids.

Concepts: Tissue, North America, Insecticide, Exponential function, Neonicotinoid, Imidacloprid, Clothianidin, Imidacloprid effects on bee population


Neonicotinoids currently dominate the insecticide market as seed treatments on Canada’s major Prairie crops (e.g., canola). The potential impact to ecologically significant wetlands in this dominantly agro-environment has largely been overlooked while the distribution of use, incidence and level of contamination remains unreported. We modelled the spatial distribution of neonicotinoid use across the three Prairie Provinces in combination with temporal assessments of water and sediment concentrations in wetlands to measure four active ingredients (clothianidin, thiamethoxam, imidacloprid and acetamiprid). From 2009 to 2012, neonicotinoid use was increasing; by 2012, applications covered an estimated ∼11 million hectares (44% of Prairie cropland) with >216,000 kg of active ingredients. Thiamethoxam, followed by clothianidin, were the dominant seed treatments by mass and area. Areas of high neonicotinoid use were identified as high density canola or soybean production. Water sampled four times from 136 wetlands (spring, summer, fall 2012 and spring 2013) across four rural municipalities in Saskatchewan similarly revealed clothianidin and thiamethoxam in the majority of samples. In spring 2012 prior to seeding, 36% of wetlands contained at least one neonicotinoid. Detections increased to 62% in summer 2012, declined to 16% in fall, and increased to 91% the following spring 2013 after ice-off. Peak concentrations were recorded during summer 2012 for both thiamethoxam (range:

Concepts: Alberta, Insecticide, Insecticides, Neonicotinoid, Imidacloprid, Clothianidin, Acetamiprid, Imidacloprid effects on bee population


Concentrations of the neonicotinoid insecticides clothianidin, thiamethoxam and imidacloprid were determined in arable soils from a variety of locations in England RESULTS: In soil samples taken from the central area of fields, concentrations of clothianidin ranged from 0.02 µg/kg to 13.6 µg/kg. Thiamethoxam concentrations were between <0.02 µg/kg and 1.50 µg/kg, imidacloprid concentrations were between <0.09 µg/kg and 10.7 µg/kg. Concentrations of clothianidin and thiamethoxam were lower in soil samples taken from the edges of fields than from the centres of fields but this difference was less pronounced for imidacloprid.

Concepts: Soil, Insecticide, Insecticides, Pesticide toxicity to bees, Neonicotinoid, Imidacloprid, Clothianidin, Imidacloprid effects on bee population


Neonicotinoids alone or in combination with pathogens are considered to be involved in the worldwide weakening of honey bees. We here present a new approach for testing sublethal and/or synergistic effects in free flying colonies. In our experiment individually marked honey bees were kept in free flying mini-hives and chronically exposed to sublethal doses of the neonicotinoid clothianidin. Additional groups of bees were challenged with Nosema infections or with combinations of the pesticide and pathogens. Longevity and flight activity of the differentially treated bees were monitored for a period of 18 days. In contrast to previous laboratory studies, no effect of the neonicotinoid treatment on mortality or flight activity could be observed. Although the lifespan of Nosema infected bees were significantly reduced compared to non-infected bees a combination of pesticide and pathogen did not reveal any synergistic effect. Our results indicate that individual bees are less impaired by neonicotinoids if kept within the social environment of the colony. The effect of such a “social buffering” should be considered in future risk assessments.

Concepts: Bacteria, Synergy, Beekeeping, Insecticide, Neonicotinoid, Imidacloprid, Clothianidin, Imidacloprid effects on bee population


Thiamethoxam, clothianidin, and imidacloprid are the most commonly used neonicotinoid insecticides on the Canadian prairies. There is widespread contamination of nectar and pollen with neonicotinoids, at concentrations which are sublethal for honey bees (Apis mellifera Linnaeus).

Concepts: Insect, Beekeeping, Insecticide, Insecticides, Neonicotinoid, Imidacloprid, Clothianidin, Imidacloprid effects on bee population


Non-target aquatic insects are susceptible to chronic neonicotinoid insecticide exposure during the early stages of development from repeated run-off events and prolonged persistence of these chemicals. Investigations on the chronic toxicity of neonicotinoids to aquatic invertebrates have been limited to a few species, under different laboratory conditions that often preclude direct comparisons of the relative toxicity of different compounds. Here, full life-cycle toxicity tests using Chironomus dilutus were performed to compare the toxicity of three commonly used neonicotinoids: imidacloprid, clothianidin, and thiamethoxam. Test conditions followed a static-renewal exposure protocol where lethal and sub-lethal endpoints were assessed on days 14 and 40. Reduced emergence success, advanced emergence timing, and male-biased sex ratios were sensitive responses to low-level neonicotinoid exposure. The 14-day LC50 values for imidacloprid, clothianidin, and thiamethoxam were 1.52 µg/L, 2.41 µg/L, and 23.60 µg/L, respectively. The 40-day EC50 (emergence) values for imidacloprid, clothianidin, and thiamethoxam were 0.39 µg/L, 0.28 µg/L, and 4.13 µg/L, respectively. Toxic equivalence, relative to imidacloprid, was estimated through a three-point response average at L(E)C(20, 50, 90) and plotted concentration-response curves. Relative to imidacloprid (TEF = 1.0), chronic (lethality) 14-day TEFs for clothianidin and thiamethoxam were 1.05 and 0.14, respectively, and chronic (emergence inhibition) 40-day TEFs were 1.62 and 0.11, respectively. These population-relevant endpoints and TEFs suggest that imidacloprid and clothianidin exert comparable chronic toxicity to C. dilutus, whereas thiamethoxam induced comparable effects only at concentrations an order of magnitude higher. However, we caution that under field conditions thiamethoxam readily degrades to clothianidin, thereby likely enhancing toxicity. This article is protected by copyright. All rights reserved.

Concepts: Toxicology, Toxicity, Insecticide, Copyright, Neonicotinoid, Imidacloprid, Clothianidin, Imidacloprid effects on bee population


Concentrations of the neonicotinoid insecticides clothianidin, thiamethoxam and imidacloprid were determined in honey collected in Spring 2013 from a variety of locations in England. The honey was produced before the moratorium in the EU on the use of neonicotinoids in pollinator-attractive crops became effective.

Concepts: United Kingdom, Insecticide, Insecticides, Pesticide toxicity to bees, Neonicotinoid, Imidacloprid, Clothianidin, Imidacloprid effects on bee population


Aquatic ecosystems are characterized by fluctuating conditions that have direct effects on aquatic communities, but also indirect influences such as changing the toxicity of chemicals. Since the effect of food quality on pesticide toxicity has rarely been studied, in the current experiment Daphnia magna juveniles supplied with four different food quality levels were exposed to a range of imidacloprid concentrations for 21 days. Food quality was expressed as carbon:phosphorus ratios of algae Pseudokirchneriella subcapitata (C:P 35, C:P 240, C:P 400 and C:P 1300). Survival, growth rates and reproduction of D. magna were monitored and the combined effects of imidacloprid exposure and the phosphorus content of algae were analyzed. A stronger effect on survival was observed at the P-deficient diet (C:P 1300), confirmed by lower EC10 values at days 7, 9, 15 and 21 compared to diets with higher phosphorus contents. Similarly, the growth rate was reduced when D. magna were supplied with algae of low phosphorus content at imidacloprid exposure conditions. The highest reproductive output was observed for D. magna fed the optimal phosphorus diet (C:P 240), both at control and exposed conditions. It was concluded that a poor food quality increased the sensitivity of non-target species to pesticide exposure, potentially leading to an underestimation of adverse effects on aquatic communities in the field. Environ Toxicol Chem © 2013 SETAC.

Concepts: Chemistry, Ecosystem, Insecticide, Aquatic ecosystem, Neonicotinoid, Imidacloprid, Ecosystems, Imidacloprid effects on bee population