Hexazinone Resistance in Red Sorrel (Rumex acetosella)

Abstract

Biannual applications of hexazinone have been applied in many lowbush blueberry fields in Nova Scotia for more than 30 years. Persistent reliance on a single herbicide chemistry may have selected for hexazinone-resistant red sorrel. The recommended rate of hexazinone (1.92 kg ai ha−1) no longer controls red sorrel in many growing regions. Six levels of hexazinone (0, 0.48, 0.96, 1.92, 3.84, and 7.68 kg ai ha−1) were applied to red sorrel plants grown in a greenhouse from seeds collected from three commercial fields and a no blueberry area to determine if they were hexazinone resistant. Red sorrel from two sites where hexazinone had not been applied regularly died at the 0.96 kg ai ha−1rate of hexazinone whereas red sorrel from two commercial fields survived at 7.68 kg ai ha−1. It is concluded that red sorrel is hexazinone-resistant in some wild blueberry fields. A portion of thepsbA gene was sequenced and it was determined that resistant plants had a Phe to Val substitution at position 255 in the D1 protein. This is the first recorded instance of hexazinone resistance in a perennial broadleaf weed in blueberry fields.