An Experimental Test of Weed-Suppressive Bacteria Effectiveness in Rangelands in Southwestern Idaho, 2016–18

Open-File Report 2019-1050
Prepared in cooperation with the Bureau of Land Management, U.S. Fish and Wildlife Service, Great Basin Landscape Conservation Cooperative, and Ada County Soil and Water Conservation District
By:  and 



Approaches and techniques for control of exotic annual grasses are a high priority in sagebrush-steppe and other rangelands. Strains of the soil bacterium Pseudomonas fluorescens (Pf) have been proposed to be selectively pathogenic to multiple species of exotic annual grasses with effects evident by the second year, and with no effect on native or desirable species including native bunchgrasses. However, scientifically defensible tests of the target and non-target/risk effects of these hypothetically weed-suppressive bacteria (WSB) strains in the field have been lacking in rangelands and other environments. We evaluated the effects of two strains of Pf WSB (D7 and MB906) sprayed on the surface in autumn 2016 at three sites in sagebrush steppe across southwestern Idaho that had cheatgrass (Bromus tectorum), medusahead (Taeniatherum caput-medusae), and other exotic annual grasses. Treatments also were replicated within each site (n=3, 8.3×8.3 meter plots) and included evaluation of the WSB strains with and without herbicides (imazapic and rimsulfuron) and with or without discing to mix surface-spray of the WSB into deeper soils. By the second year following application (spring 2018), neither strain of WSB affected exotic annual grasses, perennial bunchgrasses, or total community cover, either with WSB alone or in combination with herbicides or discing. We conclude that neither the D7 nor MB906 strains of Pf WSB have a negative effect on exotic annuals at the sites we evaluated.

Suggested Citation

Lazarus, B.E., and Germino, M.J., 2019, An experimental test of weed-suppressive bacteria effectiveness in rangelands in southwestern Idaho, 2016–18: U.S. Geological Survey Open-File Report 2019-1050, 19 p.,

ISSN: 2331-1258 (online)

Study Area

Table of Contents

  • Abstract
  • Introduction
  • Methods
  • Results
  • Discussion
  • Acknowledgments
  • References Cited
Publication type Report
Publication Subtype USGS Numbered Series
Title An experimental test of weed-suppressive bacteria effectiveness in rangelands in southwestern Idaho, 2016–18
Series title Open-File Report
Series number 2019-1050
DOI 10.3133/ofr20191050
Year Published 2019
Language English
Publisher U.S. Geological Survey
Publisher location Reston, VA
Contributing office(s) Forest and Rangeland Ecosystem Science Center
Description 28 p.
Country United States
State Idaho
Online Only (Y/N) Y
Google Analytic Metrics Metrics page
Additional publication details