Potential Exposure of Pollinators to Neonicotinoid Insecticides from the Use of Insecticide Seed Treatments in the Mid-Southern United States

Abstract

Research was done during 2012 to evaluate the potential exposure of pollinators to neonicotinoid insecticides used as seed treatments on corn, cotton, and soybean. Samples were collected from small plot evaluations of seed treatments and from commercial fields in agricultural production areas in Arkansas, Mississippi, and Tennessee. In total, 560 samples were analyzed for concentrations of clothianidin, imidacloprid, thiamethoxam, and their metabolites. These included pollen from corn and cotton, nectar from cotton, flowers from soybean, honey bees, Apis mellifera L., and pollen carried by foragers returning to hives, preplanting and in-season soil samples, and wild flowers adjacent to recently planted fields. Neonicotinoid insecticides were detected at a level of 1 ng/g or above in 23% of wild flower samples around recently planted fields, with an average detection level of about 10 ng/g. We detected neonicotinoid insecticides in the soil of production fields prior to planting at an average concentration of about 10 ng/g, and over 80% of the samples having some insecticide present. Only 5% of foraging honey bees tested positive for the presence of neonicotinoid insecticides, and there was only one trace detection (< 1 ng/g) in pollen being carried by those bees. Soybean flowers, cotton pollen, and cotton nectar contained little or no neonicotinoids resulting from insecticide seed treatments. Average levels of neonicotinoid insecticides in corn pollen ranged from less than 1 to 6 ng/g. The highest neonicotinoid concentrations were found in soil collected during early flowering from insecticide seed treatment trials. However, these levels were generally not well correlated with neonicotinoid concentrations in flowers, pollen, or nectar. Concentrations in flowering structures were well below defined levels of concern thought to cause acute mortality in honey bees. The potential implications of our findings are discussed.

Landscape and pesticide effects on honey bees: forager survival and expression of acetylcholinesterase and brain oxidative genes

“…Low concentrations of imidacloprid were reported on soybean flowers of both Jackson and Yum-Yum locations, while no neonicotinoids were found in corn and sorghum flowers (Table IV). The neonicotinoid residues in our study are much higher than what has been reported in a recent study conducted in western Tennessee (Stewart et al 2014), but this study was targeting seed treatment effects whereas our current study would be influenced by foliar-applied insecticides. The recovered foragers seemed not to have encountered the pesticides detected in the crops' flowers, as no high concentrations were detected in those bees (Table IV).…”

Sublethal Effects of Imidacloprid on Honey Bee Colony Growth and Activity at Three Sites in the U.S.

“…Regarding the treatments selected here, even in agriculturally intensive areas, such as the southeastern U.S., concentrations as high as 100 ppb have seldom been reported in pollen or nectar. Stewart et al [35] found that neonicotinoid levels in soils and wild flowers after seed treatment applications in experimental and commercial plots seldom exceeded 50 ppb. Bees exposed to high levels of imidacloprid in nectar also may simply reduce or avoid feeding on contaminated nectar, whether or not alternative forage is available [9].…”

A sublethal dose of a neonicotinoid insecticide disrupts visual processing and collision avoidance behaviour in Locusta migratoria

“…Widespread NI crop treatment has increased overall pesticide use across North America 2 , despite growing evidence of toxic effects on wild and domestic bee populations 3, 4 , aquatic invertebrates 5–7 , and insectivorous birds 8 . NIs contaminate wetlands, via runoff and snowmelt from treated fields 9 , and wildflower and soil samples near treated fields at concentrations exceeding 10 ng/g 10 .…”