New Herbicide-Resistant Downy Brome (Cheatgrass) Montguide Available

Information for this article comes from Montguide MT 201814AG. Authors include Dr. Prashant Jha from MSU Southern Agricultural Research Center and a group of County Extension Agents from Montana The complete document is available online or at the Chouteau County Extension Office. Our office is located in the green building next to the courthouse.

Herbicide-resistant plants often develop from repeated use of a single mode of action herbicide. Plants can develop resistance to additional herbicides, and then require integrated, and more costly management techniques. As of February, 2018, Group 2-resistant Downy Brome has been identified in Chouteau, Yellowstone and Carter Counties.

All Integrated Pest Management recommendations are available in the Montguide. Herbicide options for Group 2 - resistant downy brome control in a wheat-fallow rotation include the following:

• Winter Wheat: Zidua WDG at 1-2 ounces per acre. Preplant./Preemergence in the Fall. Treatment includes herbicide group 15.

• Winter Wheat: Anthem Flex at 2-4.5 ounces per acre. Preplant/Preemergence in the Fall. Treatment includes herbicide groups 14 and 15.

• Burndown or Fallow: Roundup Powermax at 32 ounces per acre (non-selective herbicide). Treatment includes group 9.

• Burndown or Fallow: Gramoxone at 32-40 ounces per acre (non-selective herbicide). Treatment includes group 22.

Herbicide options for Group 2-resistant downy brome control in a pulses include the following:

• Pulses: Assure II at 12 ounces per acre (selective herbicide). Treatment includes Group 1.

• Pulses: Select Max (Clethodim) at 16 ounces per acre (selective herbicide). Treatment includes Group 1.

Growers who suspect a Group 2-resistant weed population should contact their local MSU Extension office for instructions on submitting

a sample for testing. Testing is offered as a free service through the MSU-Southern Ag Research Center Weeds Lab: 748 Railroad Highway Huntley, MT 59037 Phone: 406-348-3400 Email: pjha@montana.edu.

Montana State University U.S. Department of Agriculture and Montana Counties Cooperating. MSU Extension is an equal opportunity/affirmative action provider of educational outreach