Bacterial Soil Amendment MB906 Shows Inconsistent Control of Invasive Annual Grasses

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In 2016, land managers began using a soil amendment called MB906, a weed-suppressive bacteria, to control invasive annual grasses, yet the success of MB906 is inconclusive.

To accurately assess responses of both native and non-native grasses, land managers applied MB906 alone and in combination with the herbicide imazapic on sagebrush-steppe landscapes that burned several months prior. MB906 did not consistently reduce target invasive annual grass cover at three southern Idaho landscapes in the three years following treatment. Interestingly, in two of three sites, MB906 appeared to reduce target grass cover – cheatgrass and medusahead – in the second year after treatment by 54 percent. However, this reduction accompanied an increase in non-target invasive grasses, so there was no overall reduction in invasive annual grasses in any year. MB906 also reduced the effectiveness of co-applied imazapic. These results do not provide strong support for MB906 as a tool for annual grass control, although the moderate effects on target annual grass cover suggest further investigation may be warranted.

Lazarus, B.E., Germino, M.J., Brabec, M.A., Peterson, L., Walker, R.N., Moser, A.M., 2020, Post-fire management-scale trials of bacterial soil amendment MB906 show inconsistent control of invasive annual grasses: Rangeland Ecology and Management,

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