Quantification of imidacloprid uptake in maize crops

Area of Science:

• Agricultural Science
• Environmental Science
• Toxicology

Background:

• Imidacloprid is a widely used systemic insecticide, particularly for seed treatment in crops like maize, sunflower, and rape.
• Concerns exist regarding the impact of neonicotinoid insecticides on non-target organisms, including pollinators.

Purpose of the Study:

• To quantify imidacloprid residues in field-grown maize at the pollen shed stage.
• To assess the risk posed to honeybees foraging on imidacloprid-treated maize using exposure and effect concentration ratios.

Main Methods:

• Analysis of imidacloprid in maize plant parts (stems, leaves, male flowers, pollen) using Liquid Chromatography coupled with tandem Mass Spectrometry (LC/MS/MS).
• Samples were collected from French maize fields between 2000 and 2003.
• Risk assessment was performed using Probable Exposure Concentrations (PEC) and Predicted No-Effect Concentrations (PNEC) for honeybees.

Main Results:

• Imidacloprid concentrations in maize ranged from <0.1 µg/kg to 33.6 µg/kg.
• Average imidacloprid levels were 4.1 µg/kg in stems/leaves, 6.6 µg/kg in male flowers, and 2.1 µg/kg in pollen.
• PEC/PNEC risk ratios for foraging honeybees on treated maize ranged from 500 to 600.

Conclusions:

• Maize treated with imidacloprid seed dressing presents a high risk to honeybees.
• Elevated imidacloprid exposure in maize crops may be a significant factor contributing to honeybee colony decline.
• Further research and regulatory evaluation are warranted to mitigate risks to pollinators.