Presenter: Anabel Dombro, MSc Candidate, University of Alberta

Annual bromegrasses are prevalent weeds on North American rangeland and have particularly affected the Great Basin and southern Great Plains of the U.S. Annual brome has been found to change plant community structure and function, lowering desirable and overall forage production, negatively affecting mammal and bird habitat, and causing frequent fires. While the extent of annual brome on Canadian rangeland has not been documented in as much detail as the U.S., records indicate it is spreading into the northern Great Plains, leading to concerns about the future status of Canada’s mixedgrass prairie. Control of these invasive species is of interest to land managers when looking to improve or maintain rangeland function. Field trials at two locations in the dry mixedgrass prairie of southeast Alberta compared the effects of four rates of indaziflam (0, 40, 80 or 160 g ai ha-1) applied at two times (fall or spring) on annual-brome invaded native grassland. Biomass responses of brome and other vegetation were assessed over 3 years. Fall indaziflam treatment provided quicker control of brome than spring treatment. The lowest indaziflam rate, 37.5 g ai/ha was unreliable at controlling brome, while the recommended rate of 75 g ai/ha controlled brome biomass and density at both sites in both 2021 and 2022 when it was sprayed in the fall. Indaziflam was still providing significant brome control in the final year of the study, 2022, and in this year several treatments had zero brome density or biomass, indicating indaziflam’s potential for long-term control. Perennial grass biomass increased under one treatment rate. The project also looked at the effects of indaziflam on non-target native species with a field study and two greenhouse studies which looked at how indaziflam impacted native perennial grass root growth and the native perennial seed bank.

This webinar is part of the Society for Range Management, Pacific Northwest Section, BC Chapter's Fall 2022 Home on the Range webinar series showcasing projects and case studies of professionals and students in the field of range management.