Weed Control in Southern Highbush Blueberry with S-metolachlor,Flumioxazin, and Hexazinone

Field studies were conducted in 2010, 2011, and 2012 at a commercial blueberry farm near Burgaw, NC to determine weed control and crop tolerance to S-metolachlor and flumioxazin alone or mixed with hexazinone. Herbicides were applied pre-budbreak and postharvest. Pre-budbreak applications consisted of hexazinone at 1.1 or 2.2 kg ai ha^?1, S-metolachlor at 1.4 or 2.8 kg ai ha^–1, and flumioxazin at 215 g ai ha^–1 alone and tank mixes of hexazinone or flumioxazin plus S-metolachlor. Additional treatments consisted of flumioxazin (215 g ha^–1), flumioxazin plus S-metolachlor (1.4 and 2.8 kg ha^–1), or hexazinone (1.1 kg ha^–1) plus S-metolachlor (1.4 and 2.8 kg ha^–1) applied pre-budbreak and followed by (fb) a postharvest application of flumioxazin (215 g ha^–1). Herbicide programs containing flumioxazin resulted in greater Maryland meadowbeauty control (73%) 5 to 6 weeks after treatment (WAT) than herbicide programs containing hexazinone at 1.1 or 2.2 kg ha^–1 (37% and 39%, respectively). Needleleaf rosette grass control remained ≥94% for all herbicide programs through 2 WAT. Hexazinone at 1.1 kg ha^–1 provided greater needleleaf rosette grass control (87%) than flumioxazin (71%) 5 to 6 WAT. Meadowbeauty and needleleaf rosette grass control by all herbicide programs was poor (≤39% and ≤57%, respectively) 16 to 18 WAT. Two weeks after post-harvest applications, herbicide programs receiving a post-harvest flumioxazin application had greater meadowbeauty and needleleaf rosette grass control (78% and 84%, respectively) than those programs without a post-harvest flumioxazin application (43% and 71%, respectively).