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

Authors: WAYMENT, DARCEY - Nicholls State University; LEDET, HARLEY - Nicholls State University; TORRES, KYLIE - Nicholls State University; White, Paul

Submitted to: Journal of Environmental Science and Health
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/24/2020
Publication Date: 2/11/2021
Citation: Wayment, D.G., Ledet, H.J., Torres, K., White Jr, P.M. 2021. Soil dissipation of sugarcane billet seed treatment fungicides and insecticide using QuEChERS and HPLC. Journal of Environmental Science and Health. 56(2):188-196.
DOI: https://doi.org/10.1080/03601234.2020.1858685

Interpretive Summary: Sugarcane seed pieces, or billets, can be treated with chemicals designed to improve their growth. The seed pieces are dipped in solutions containing fungicide and/or insecticide prior to planting to provide protection against soil borne pests. Research demonstrates that treating billet seed pieces increases the yield of the subsequent sugarcane crop. However, the fate of the applied chemicals once the billets are planted in soil is unknown. Therefore, the purpose of this experiment was to measure the decomposition of billet seed treatment chemicals in a soil used to grow sugarcane. Soil was treated with fungicide or insecticide and the levels of each chemical was monitored for over 100 days. The data were analyzed and used to compute the half-life of each separate chemical in soil, which were between 39 and 275 days. Overall, these chemicals decomposed on a medium to long time frame and should provide protection for the billet seed pieces against soil-born pests. However, the longer times may indicate that some potential for environmental contamination is possible if chemicals are not used properly. This is the first report for several of these pesticides related to the aerobic dissipation in soils used to grow sugarcane.

Technical 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 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.