Weed-Suppressive Soil Bacteria to Reduce Cheatgrass and Improve Vegetation Diversity on ITD Rights-of-Way

Transportation departments are challenged by the invasion of downy brome (cheatgrass) and medusahead. The reduction of downy brome (cheat grass) by Weed Suppressive Bacteria (WSB) Pseudomonas fluorescens strain ACK55 was evaluated on roadsides of I-84, I-86 and US-95 in Idaho. Bacteria were produced and sprayed on 1-acre plots at eleven locations at seven sites in the fall of either 2014, 2015 or 2016 at 10⁹ colony forming units (cfu)/m². The vegetation in each plot at each location was monitored in the spring and fall of each year using Sample Point. Sample Point is a digital method of monitoring vegetation across landscapes coupled with a software package that estimates cover of species or groups of plants. Percent cover of species (native and invasive), the total cover of vegetation, litter, rock, cryptogamic crust, bare soil, and geographic information system (GIS) coordinates were recorded. The bacteria reduced downy brome (cheatgrass) by 30 to 97 percent of the control. Medusahead patches were evident in the control plots, but not found after the bacteria were applied. The volume and timing of WSB application is critical to the successful, long-term reduction and exclusion of downy brome (cheatgrass) and medusahead. Late fall applications, when air and soil temperatures were cool (below 50°F), rains were prevalent and skies were overcast, had the highest success. The greatest success with long-term reductions of downy brome (cheatgrass) and medusahead was on lands with mixed populations of native plants and moderate weed infestations. Because of its selectivity, this bacterium can be used in management of the invasive weeds downy brome (cheatgrass) and medusahead on Idaho Transportation Department (ITD) roadsides.

  • Record URL:
  • Corporate Authors:

    Washington State University, Pullman

    USDA-Agricultural Research Service
    Pullman, WA  United States 

    Idaho Transportation Department

    Division of Highways, Resource Center, Research Program
    P.O. Box 7129, 3211 State Street
    Boise, ID  United States  83707-7129

    Federal Highway Administration

    1200 New Jersey Avenue, SE
    Washington, DC  United States  20590
  • Authors:
    • Kennedy, Ann C
  • Publication Date: 2017-6


  • English

Media Info

  • Media Type: Digital/other
  • Edition: Final Report
  • Features: Appendices; Figures; Glossary; Maps; Photos; References; Tables;
  • Pagination: 117p

Subject/Index Terms

Filing Info

  • Accession Number: 01668737
  • Record Type: Publication
  • Report/Paper Numbers: FHWA-ITD-17-258, RP 258
  • Contract Numbers: 58-2090-6-011
  • Created Date: Mar 23 2018 11:01AM