Hay Swather Applied Flutriafol to Alfalfa Stubble: Residue Levels in Immediately Harvested Hay and Subsequent Flood Irrigation Water
ISSN 2158-9429
Volume 17, Issue 2 - December 2024
Editor: Linda Chalker-Scott
Abstract
The fungicide TopGuard Terra® (active ingredient = flutriafol) was applied at top labeled rate of 12 oz./acre to alfalfa (Medicago sativa L.) stubble/bare soil via swather at cutting to determine if such applications would result in flutriafol residues of harvested alfalfa placed upon immediately treated stubble would exceed the established alfalfa hay tolerance level of 70 parts/million (ppm). Residue levels in flood irrigation water moving across treated areas were obtained as such data were also unavailable, and concerns existed for product movement with this irrigation method and potential accumulation at field end for product usage in California. Flutriafol residues from windrowed hay that had been in contact with treated stubble and collected two days post application averaged 8.97 ppm, ranging from 5-16, far below the 70 ppm tolerance level. Sampling of flood irrigation waters in first subsequent irrigation after application and post baling noted very low flutriafol levels (0.12-0.30 ppm) contained in irrigation waters in treated areas. Such residues were thought to be due to fine soil particles adhering to and contained within flood irrigation water movement across field, rather than disassociation from soil. Residue levels remained low as flood irrigation waters proceeded across field, without evidence of accumulation at end of field. Data indicate that swather application of TopGuard Terra® and other fungicides containing flutriafol is a viable technique and could be added to product labeling and result in reduced application costs.
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