Browsing by Subject "Imidacloprid"

Now showing 1 - 3 of 3
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    Chronic exposure of imidacloprid and clothianidin reduce queen survival, foraging and nectar storing in colonies of Bombus impatiens
    (2013-07) Scholer, Jamison D.
    The 20 year research focus on residue levels below 10 ppb of neonicotinyl insecticides found in nectar and pollen of seed-treated crops (corn, canola, and sunflower) has not demonstrated a reduction in bee colony health in most field studies. However, the label rate of neonicotinyl use on crops and landscape plants is much higher than seed treatments. In addition, crops and flowers can be retreated multiple times a season which can contribute to chronic exposure to bees at higher residue levels. In an 11 week greenhouse cage study with queenright colonies of Bombus impatiens Cresson, provided 0, 10, 20, 50 and 100 ppb imidacloprid or clothianidin in sugar syrup, neither neonicotinyl reduced production of brood, workers, and queens. Male production decreased in 10-100 ppb imidacloprid and 50-100 ppb clothianidin treatments. However, starting at 6 weeks queen mortality was significantly higher in 20-100 ppb imidacloprid or clothinaidin. The largest impact was the reduction in worker movement, consumption, number of syrup filled wax pots, and the addition of wax to the colony, which resulted in reduced colony weight. Queens and nest bees fed on the sugar syrup stored in wax pots that were filled prior to the start of the experiment. Foraging bees did not return sugar syrup to the nest, but remained on the floor of the flight box. We argue that queen mortality at 20, 50, and 100 ppb was related to lack of syrup in storage pots. We speculate that as queens started to die at week 6, workers in 20-100 ppb treatments produced fewer males and instead provisioned cells to produce new queens, since queen production was not reduced at higher doses, but male production was reduced. Since neonicotinyls in this and other studies were shown to reduce food consumption and foraging, wild bumblebee colonies that depend on workers to forage will be negatively affected by exposure to imidacloprid above 20 ppb. Solitary bees will be greatly impacted as the foraging queens solely provision the larvae.
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    Evaluation of Neurobehavioral Abnormalities and Immunotoxicity after Oral Imidacloprid Exposure in Domestic Chickens (Gallus gallus domesticus)
    (2019-05) Franzen-Klein, Dana
    Neonicotinoid pesticides may have negative effects on non-target species at environmentally plausible exposure doses. The objective of the present study was to quantify neurobehavioral abnormalities and immunotoxicity due to oral imidacloprid exposure in birds. Domestic white leghorn chickens (Gallus gallus domesticus; n=120) were exposed to imidacloprid by gavage once daily for 7 consecutive days at 0, 0.03, 0.34, 3.42, 10.25, and 15.50 mg/kg. The severity and duration of neurobehavioral abnormalities were recorded, and immune function was assessed with 7 standard functional assays. Immunotoxicity was not detected. Temporary neurobehavioral abnormalities were observed in a dose-dependent manner, including generalized whole-body muscle tremors, ataxia, and depressed mentation ranging from mild depression to a complete lack of response to external stimulation. The effect dose value for the presence of any neurobehavioral abnormalities in 50% of the test group (ED50) was 4.63 mg/kg/day. The ED50 for an adjusted score that included both the severity and duration of neurobehavioral abnormalities was 11.27 mg/kg/day. The no observed adverse effect level (NOAEL) and lowest observed effect level (LOEL) were 3.42 mg/kg/day, and the lowest observed adverse effect level (LOAEL) was 10.25 mg/kg/day. While immunotoxicity was not demonstrated in the present study, it cannot be ruled out. The observed neurobehavioral abnormalities were severe at the higher doses and may impair survival of free-living gallinaceous birds.
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    Neonicotinoid Hydrolysis and Photolysis: Rates and Residual Toxicity
    (2018-05) Todey, Stephen
    Neonicotinoid insecticides are currently the most widely used class of insecticides worldwide, accounting for 25% of total insecticide use. They are registered in 120 countries for use on more than 140 crops. Concern has grown, however, over their widespread detection in global surface waters, soil, finished drinking water, and wastewater, and for their potential role in colony collapse disorder in honey bees. This work set out to examine hydrolysis and photolysis reaction rates of neonicotinoids, as well as to identify reaction products and determine the toxicity of the reaction products on mosquitoes. Hydrolysis rates were tested between pH 4 and pH 10. Reaction rates were pseudo-first order and highly pH dependent. Calculated half-lives ranged from >1000 days to 10 days. Divalent metal ions (Cu2+, Ni2+, Zn2+) and minerals (kaolinite, goethite, TiO2) were found to have little to no effect on neonicotinoid hydrolysis. Experiments from pH 4 to pH 10 revealed a non-elementary rate law for neonicotinoid degradation, with the hydroxide concentration being raised to a power of 0.55 ± 0.09. Nitenpyram, imidacloprid, thiamethoxam, and clothianidin were found to undergo direct photolysis, with quantum yields of 0.025 ± 0.001, 0.0119 ± 0.0001, 0.0167 ± 0.0002, and 0.0133 ± 0.0001, respectively. Acetamiprid degraded very slowly via direct photolysis, but was found to undergo indirect photolysis due to reaction with OH∙ with a bimolecular rate constant of 1.7 ± 0.2×109 M-1 s-1. Reaction products were identified for all reactions, with the urea derivative as the most commonly detected product. Toxicity experiments on mosquitoes indicate no residual toxicity from hydrolysis or photolysis products, which may be expected given the removal of the pharmacophore during reactions. While abiotic reaction products were found to be non-toxic, results from experimental work indicates long environmental half-lives for the tested neonicotinoids, which may help to explain their observed persistence in environmental matrices.