Soil dissipation of sugarcane billet seed treatment fungicides and insecticide using QuEChERS and HPLC

Abstract

Chemical treatment of sugarcane seed with fungicides and insecticides prior to planting increases yields of cane and sugar for the perennial, annually harvested crop. However, the fate of the applied chemicals is unknown. Therefore, the purpose of this study was to measure the aerobic dissipation of selected billet seed treatment chemicals in a mineral sugarcane soil from Louisiana. Soil samples from the surface 15 cm were treated with either thiamethoxam, azoxystrobin, fluxapyroxad, propiconazole, or pyraclostrobin and monitored over 100 days under laboratory conditions. Insecticide and fungicide levels were determined by high performance liquid chromatography. Dissipation data were fitted to four kinetic models: simple first-order (SFO), first order multi-compartment (FOMC), double-first order in parallel (DFOP), and hockey-stick (HS). The dissipation half-life (DT₅₀) of thiamethoxam, azoxystrobin, fluxapyroxad, propiconazole, or pyraclostrobin were 275, 100, 144, 74, and 39 d, respectively. Overall, the DT₅₀ for the pesticides in the study indicated medium to long persistence in soil under the conditions of the experiment. This is the first report for several of these pesticides related to the aerobic dissipation in soils used to grow sugarcane.

Keywords:

• Chemical seed treatment
• conazole fungicides
• neonicotinoid insecticide
• pyrazole-carboxamide
• soil dissipation
• strobilurin
• sugarcane

Acknowledgments

The laboratory assistance of Mr. Conner Brochon, Mr. Chris Adams, and Mr. Derek Landrum was greatly appreciated. Mention of trade names or commercial products is solely for the purpose of providing specific information and does not imply recommendation or endorsement by the U.S. Department of Agriculture.

Additional information

Funding

Funding was provided by Nicholls State University and the USDA-Agricultural Research Service Sugarcane Research Unit in Houma, LA. Funding for the purchase of the HPLC system was provided by the Louisiana Board of Regents.