Comparison of the Photodegradation of Imazethapyr in Aqueous Solution, on Epicuticular Waxes, and on Intact Corn (Zea Mays) and Soybean (Glycine Max) Leaves

Abstract

A direct, controlled comparison of the photodegradation of imazethapyr has been made between imazethapyr in aqueous solutions, imazethapyr on the surface of epicuticular waxes of corn and soybean plants, and imazethapyr on the surface of intact corn and soybean plant leaves. In some experiments, the imazethapyr solutions were allowed to evaporate partially or fully after application to better model environmental conditions. The photodegradation of imazethapyr was fastest in aqueous solutions (k = 0.16 ± 0.02 h⁻¹) and slowest on the surface of corn and soybean plants (k_corn = 0.00048 ± 0.001 h⁻¹ and k_soy = 0.00054 ± 0.003 h⁻¹). Experiments allowing evaporation during irradiation have intermediate rate constants (e.g., k_corn = 0.082 ± 0.005 h⁻¹). Finally, identification of photoproducts was also examined on epicuticular waxes of corn and soybean plants for the first time.

Keywords:

• Imazethapyr
• epicuticular wax
• photodegradation
• soybean (Glycine max)
• corn (Zea mays)
• solar simulator

Acknowledgements

We extend our gratitude to Dr. Dwight Stoll for the use of his chromatographic and mass spectrometry equipment and expertise, Brittany Courteau for collecting samples, and Jonna Berry for building the solar simulator. The mass spectrometer used in this work was provided to Gustavus Adolphus College as part of an Agilent Technologies Thought Leader Award. Funding for this work comes from the National Science Foundation (#1213236).

Additional information

Funding

This research was supported by the National Science Foundation (Grant Number: 1213236).