Downy brome.
Downy brome.

The U.S. oil and gas industry has grown rapidly in the past decade, creating thousands of new jobs across a broad geography. The digging performed around rigs and pipelines, though, does have a downside. It disturbs the soil and surrounding native vegetation, giving invasive weeds a chance to flourish.   

“In western North America, many energy developments coincide with infestations of downy brome, a nonnative annual grass that grows very aggressively,” says Danielle Johnston, Ph.D., a researcher with both Colorado Parks and Wildlife and Colorado State University.

In an article featured in the most recent issue of Invasive Plant Science and Management, Johnston describes a multiyear field study she conducted in Colorado’s Piceance Basin, a region experiencing extensive natural gas development. Downy brome is thriving in the region and crowding out native sagebrush plants.

Johnston’s research evaluated the effect of various weed control strategies on plant communities following disturbances to the soil and native vegetation. She found that tillage treatments, including disking and rolling, had little long-term effect on the density of downy brome; weed seedlings quickly rebounded to pretreatment levels.

When the selective herbicide imazapic was applied in a mixture with glyphosate, though, the density of downy brome seedlings remained low throughout the growing season. Three years later, native shrub cover was eight times higher on herbicide-treated plots than on control plots where no herbicides were used. 

In addition to the use of imazapic, Johnston recommends the following weed control strategies to reduce the impact of downy brome in areas where the soil will be disturbed:

  • Treat downy brome patches before any digging is done in order to reduce seed production.
  • Immediately after the digging, line the edges of the area with brush, a trench or other seed-dispersal barrier.
  • Control weeds that emerge in the disturbed area before they produce seed.
  • Disk and firm the soil to bury downy brome weed seeds just before restoring native plants so the native species will have time to become established before any downy brome emerges.

Full text of the article “Downy Brome (Bromus tectorum) Control for Pipeline Restoration” is available in Volume 8, Issue 2 of the journal Invasive Plant Science and Management.