Strains of the widespread bacterium Pseudomonas fluorescens have reportedly reduced root growth of exotic grasses such as cheatgrass, medusahead, and jointed goat grass, yet scientifically defensible tests of the target and non-target effects of these weed-suppressive bacteria strains in the field are needed. USGS researchers Matthew Germino and Brynne Lazarus evaluated the effects of two strains of P. fluorescens (D7 and MB906) on exotic annual grasses at three sagebrush steppe sites with contrasting soils and climate. Neither bacteria strain affected exotic annual grasses, perennial bunchgrasses, or total community cover, either applied alone or in combination with herbicides or discing. Weed-suppressive bacteria have received considerable attention and are being applied across large rangeland areas, but these results indicate a low likelihood of reducing annual grasses.
 

Germino, M.J., Lazarus, B.E., 2019, Weed-suppressive bacteria have no effect on exotic or native plants in sagebrush-steppe: Rangeland Ecology and Management, https://doi.org/10.1016/j.rama.2019.10.004