Persistence and degradation of the herbicide hexazinone in soils of lowbush blueberry fields in Nova Scotia, Canada

Hexazinone is a broad spectrum herbicide used primarily in forestry, industrial and right-of-way weed control. Hexazinone is very water soluble. It readily leaches in soils and, depending on rainfall and slope, can be transported laterally following surface applications. Eight metabolites were extracted from UC-hexazinone treated soils and metabolite C was the major metabolite at each location. Hexazinone is degraded primarily by microorganisms in the soil with little degradation occurring under sterile or anaerobic conditions. The native lowbush blueberry (Vaccinium angustifolium) is tolerant to hexazinone at rates that give selective control of many weedy species associated with this crop. This blueberry is an important fruit crop of Maine and the Eastern Canadian provinces where commercial fields have been developed by management of wild stands originating from forests or abandoned farmland. Hexazinone is now widely used in all blueberry producing areas with thousands of hectares treated annually. The following study examines the fate of this UC-labelled herbicide in several typical soil types in the field and under laboratory conditions.