Weed-Suppressive Bacteria Did Not Control Bromus tectorum

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Recent trials using a bacterial bioherbicide known as D7 have had mixed results in controlling invasive annual grasses in rangelands. 

USGS and USFWS researchers conducted two case studies in south-central Washington testing D7’s ability to control of B. tectorum, or cheatgrass: one involved mixing D7 with native seeds sown after a fire and the other involved spraying D7 on a native community with high abundance of B. tectorum. Foliar cover, biomass, and density of B. tectorum with sprayed or seed mixture applications did not differ between D7-treated and untreated areas. D7 as a seed mixture did not significantly impact densities of native seedlings. Results contrasted with previous D7 studies that showed effective control of B. tectorum within three years of treatment. Although this work did not demonstrate effective control of B. tectorum by D7, this negative result can be useful to document D7’s effectiveness at different rangeland sites. 

Pyke, D.A., Shaff, S.E., Gregg, M.A., Conley, J.L., 2019, Weed-suppressive bacteria applied as a spray or seed mixture did not control Bromus tectorum: Rangeland Ecology and Management, https://doi.org/10.1016/j.rama.2019.11.001

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