Evaluation of season-long chemical controls and an experimental control of bindweed in established blueberry plantings

We hypothesize that the use of quinclorac (commercial name, Quinstar 4L), a group 4 herbicide registered for pre-emergent control of perennial broadleaf weeds and annual grasses, and the use of nitrification inhibitors as an experimental nutrient management strategy, will provide adequate control of weeds when compared to a ‘current practice’ herbicide treatment in an established blueberry field. The established blueberry field is located at the UMass Cold Spring Orchard in Belchertown, MA. Our experimental treatments will consist of an application of quinclorac for perennial broadleaf control tested at a ‘full’ (0.37 lb/acre) and ‘half’ (0.19 lb/acre) rate, tank-mixed with flumioxazin (commercial name, Chateau EZ) for annual grass and annual broadleaf weed control at a ‘full’ (12 oz/acre) rate (Table 1). By testing at two different rates (half and full), we will measure the efficacy of quinclorac in sandy soils typical of New England. Ammonium sulfate will be used as fertilizer across all treatments. The nitrification inhibitor 3,4-dimethylpyrazole phosphate (DMPP), will be applied with fertilizer applications as the experimental cultural weed management strategy. Both rates of quinclorac will also be combined with nitrification inhibitors to test for interactions between these strategies. Treatments will be compared to a negative control with mulch serving as the only cultural weed management strategy, as well as a positive control ‘current practice’ herbicide regimen. The ‘current practice’ herbicide regimen will be composed of one application of a pre-emergent herbicide targeting annual weeds, one to three post-emergent herbicide applications during the growing season for control of perennial weeds, and one pre-emergent herbicide application in the fall, as well as a traditional woodchip mulch. All herbicide applications in the ‘current practice’ treatment will be determined based on the weed species identified during weed scouting throughout the growing season. In all herbicide treatments, the new formulation of Chateau EZ will be used as a pre-emergent treatment for annual broadleaf weeds and annual grasses.