Temporal Profile of Neonicotinoid Concentrations in Cotton, Corn, and Soybean Resulting from Insecticidal Seed Treatments

Adam Whalen,Scott D Stewart,Fred R Musser,Donald R Cook,Gus M Lorenz,Jeff Gore,Jeffrey W Harris,Natraj Krishnan,Angus L Catchot

doi:10.3390/agronomy11061200

Abstract

Neonicotinoids have been implicated as a contributing factor to the observed decreases in honey bee populations. It has been suggested that honey bees can be exposed to seed-treated neonicotinoids through pollen and nectar from treated plants. To investigate the uptake and persistence of neonicotinoids in plant tissue and soil, we conducted seed treatment trials with corn, cotton, and soybean planted in Mississippi, Arkansas, and Tennessee during the 2013 and 2014 growing seasons. Leaf tissue was collected and analyzed beginning shortly after emergence until plants began to flower to better understand how neonicotinoid concentrations change in plant tissues over time. The youngest leaf in the terminal of the plant was sampled as an indicator of the neonicotinoid concentrations within the plant. Soil samples were also collected and analyzed for neonicotinoid concentrations at the first and last sampling dates. The mean clothianidin concentrations in corn treated with Poncho® 250, 500, and 1250 seed treatments declined by 99.3, 99.3, and 97.8 percent, respectively, as the plants developed from seedlings to reproductive plants. The mean concentration of imidacloprid detected in Aeris®-treated cotton decreased by 99.6 percent during the sampling period. For cotton seed treated with Avicta® Duo, the mean concentrations of thiamethoxam and clothianidin in leaf tissue declined by 99.9 and 100 percent, respectively, by the time flowering occurred. There was a 99.9 percent reduction in the mean concentration of thiamethoxam by the time of flowering in leaf tissue from soybean treated with a CruiserMaxx® seed treatment. Mean clothianidin concentrations completely diminished (<1 ng/g) in CruiserMaxx®- and Poncho®/VOTiVO®-treated soybean plants by the time plants reached reproductive growth. The data for neonicotinoid concentrations in the soil were more variable than leaf tissue samples, and the reduction in neonicotinoid concentrations in leaf tissues did not closely correlate with concentrations in the soil. Our results suggest that neonicotinoid insecticides, when used as seed treatments in these crops, decline rapidly throughout vegetative growth stages. However, the biological impact on target or non-target arthropods was not examined.

Highlights

Introduction distributed under the terms andThe neonicotinoids are a widely employed class of insecticides used in row crop agriculture to protect against a broad range of economically important pests including piercing and sucking insects as well as some below-ground coleopteran and lepidopteran pest species [1]
Concentrations of clothianidin in corn leaf tissue from seed-treated corn dramatically decreased from the initial concentrations detected to what was detected at the VT growth stage
These samples contained a mean concentration of clothianidin of 12 ± 4.7 ng/g which was 99.3 percent less than the concentration of clothianidin initially detected at V1

Summary

Introduction

Introduction distributed under the terms andThe neonicotinoids are a widely employed class of insecticides used in row crop agriculture to protect against a broad range of economically important pests including piercing and sucking insects as well as some below-ground coleopteran and lepidopteran pest species [1]. Usage of this insecticide class has dramatically increased across the United States [2] This class of chemicals has been rapidly adopted because of several key attributes including their systemic nature and persistence, ease of application, low mammalian toxicity, and efficacy against target pests resistant to other insecticide classes [3]. In the United States, one of the primary uses of neonicotinoids in agriculture is as a seed treatment that is fixed to the outer coating of crop seed prior to planting [3]. This prophylactic approach serves more as a preventative treatment for potential pest problems rather than a traditional integrated pest management tactic [2]. Neonicotinoid seed treatments are one of the few control options available to prevent yield and economic losses from many early-season pests [4]

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