Correction: Assessment of Chronic Sublethal Effects of Imidacloprid on Honey Bee Colony Health

Biochar changed the distribution of imidacloprid in a plant-soil-groundwater system

The use of biochar has increased, as its physicochemical properties reduce the adverse effects of pesticides. However, few studies have comprehensively investigated the effects of biochar on the distribution of pesticides in a plant-soil-groundwater system. In this study, a biochar produced from rice straw at 550 °C was chosen, and column experiments with five rated of biochar application (application rates = 0.0, 1.0, 2.0, 3.0, and 4.0% w/w for B0-B4, respectively) were conducted to investigate the capacity of biochar to immobilize imidacloprid (IMI) in soil, thereby decreasing its uptake by plants and leaching from soil into groundwater. Our results showed that IMI in plants, leached from soil, and detected in soil accounted for 3.78, 1.76, and 36.4% of the total IMI input, respectively, and the biochar treatments dramatically decreased the IMI distribution to 0.57, 0.11, and 13.4%, respectively. By contrast, the percentage of undetected IMI increased from 58.1% in the B0 treatment to an average of 86.0% in the biochar treatments. Biochar treatments increased IMI immobilization in soil, which could be related to the increased soil carbon content, surface area, cation exchange capacity. This study indicates that biochar with characters of high surface area and porosity can stabilize IMI and reduce its potential to harm plants and groundwater.

Translocation and metabolism of imidacloprid in cabbage: Application of 14C-labelling and LC-QTOF-MS

Imidacloprid (IMI) is a widely used neonicotinoid insecticide effective against sucking and some chewing insects. Translocation and metabolism of IMI in plants are related to food safety. In this study, ¹⁴C-labeled IMI was used to investigate its translocation, transformation, radioactive IMI metabolites and possible metabolic pathways in cabbage. The amount of IMI accumulated in the edible part of cabbage accounted for 80.3-95.4% of the applied amounts by foliar application. There was a tendency to transport from edible parts to inedible parts. The proportions of extractable IMI decreased gradually from 92.4% to 83.0% in edible parts, greater than that in inedible parts over the experiment (0-19 days), while the bound residues showed an opposite trend. The half-life of IMI was determined as 33.0 and 63.0 days in the edible parts and whole plant, respectively. Five radioactive components including the parent IMI were detected by HPLC-LSC. The relative content of M1 was less than 0.01 mg kg^-1, which was not required to identify according to the metabolic scheme proposed by the US Environmental Protection Agency. The metabolites N-nitro(1-6-chloro-3-pyridylmethyl)-4,5-dihydroxyimidazol-2-imine (M2), N-nitro(1-6-chloro-3-pyridylmethyl)-4/5-hydroxyimidazole-2-imine (M3) and 1/3-(1-6-chloro-3-pyridylmethyl)-2,4-imidazodione (M4) were identified by LC-QTOF-MS. The primary metabolism of IMI in cabbage included hydrolysis and oxidation. The residue level and daily intake values of IMI in cabbage were estimated to be 0.033-0.078 mg kg^-1 and 9.56-20.01 ng d^-1 kg^-1, respectively, which were far below the maximum residue level and allowable daily intake values.

Compound and Dose-Dependent Effects of Two Neonicotinoid Pesticides on Honey Bee (Apis mellifera) Metabolic Physiology

Use of neonicotinoid pesticides is now ubiquitous, and consequently non-targeted arthropods are exposed to their residues at sub-lethal doses. Exposure to these neurotoxins may be a major contributor to poor honey bee colony health. Few studies have explored how sub lethal exposure to neonicotinoids affects honey bee metabolic physiology, including nutritional and energetic homeostasis, both of which are important for maintaining colony health. Reported here are results from a study of chronic oral exposure of honey bees to two sub lethal concentrations of clothianidin and imidacloprid. Neonicotinoids altered important aspects of honey bee nutritional and metabolic physiology in a compound and dose-dependent manner; both compounds at low doses reduced honey bee body weight. Low-dose clothianidin exposure resulted in bees having protein, lipids, carbohydrates, and glycogen levels similar to newly emerged bees. High-dose clothianidin exposure lowered lipids and glycogen content of bees. High-dose imidacloprid exposure resulted in bees having depressed metabolic rate. Low-dose imidacloprid exposure resulted in bees consuming low and high levels of protein and carbohydrate rich foods, respectively. Results suggest neonicotinoids interfere with honey bee endocrine neurophysiological pathways. Compound and dose-dependent effects might represent respective chemical structural differences determining an observed effect, and thresholds of compound effects on honey bee physiology.