Broadleaf Weed Control and Crop Safety with Premixed Pyrasulfotole and Bromoxynil in Winter Wheat

For more than two decades acetolactate synthase (ALS) inhibiting herbicides have been the major weed control tools in winter wheat which resulted in selection of resistant weeds to those herbicides. Premix of pyrasulfotole & bromoxynil (Huskie?), a relatively new herbicide, was registered for use in wheat in 2008. Pyrasulfotole inhibits 4-hydoxyphenylpyruvate dioxygenase (HPPD) enzyme in susceptible plants and is the first significant new mode of action for use in cereals for more than two decades. Field experiments were conducted from 2007 to 2010 at two locations in Kansas, USA to test the efficacy of pyrasulfotole & bromoxynil for broadleaf weed control and crop safety in winter wheat. Treatments included pyrasulfotole & bromoxynil alone at 253 g·ai·ha-1 and tank mixtures of pyrasulfotole & bromoxynil at 207 g·ai·ha-1 with MCPA at 280 g·ai·ha-1, dicamba at 140 g·ai·ha-1 or metsulfuron-methyl at 4.2 g·ai·ha-1. Herbicides were applied postemergence in fall and spring seasons. Pyrasulfotole & bromoxynil alone or in combination with tank-mix partners, regardless of application time, controlled flixweed, blue mustard, bushy wallflower and field pennycress 98% or more. Henbit control was better when pyrasulfotole & bromoxynil treatments were applied in fall than spring (≥98% vs ≥67%). Pyrasulfotole & bromoxynil alone applied in spring was not effective on wild buckwheat, but tank mixing with dicamba or metsulfuron-methyl controlled it 84% or more. Pyrasulfotole & bromoxynil alone or as tank mixture caused little (≤7%) or no injury to wheat and the injury did not influence wheat grain yields. Based on excellent control of broadleaf weeds evaluated, pyrasulfotole & bromoxynil is an alternative tool to control ALS-inhibitor resistant weeds in winter wheat. Fall season application and tank mixing with other herbicides are desirable for effective and broad spectrum weed control.