We conducted two case studies testing effectiveness of a soil-borne bacteria, Pseudomonas fluorescens strain D7, in controlling Bromus tectorum (cheatgrass) and in affecting the density of sown desirable seedlings. We conducted two case studies testing D7’s ability to control of B. tectorum (cover, biomass and density) when mixed with native seeds sown after a fire and when sprayed on a native community with high abundances of B. tectorum. Each case study area (162 ha) compared treatments with D7 present and absent and was replicated four times (20.3 ha each) in a completely randomized design. Response variables (foliar cover, aboveground biomass, and density of B. tectorum; density of sown native plants) were measured pretreatment for the sprayed area and each year for three years after treatment at both study areas and were evaluated as a repeated measures analysis. Foliar cover, biomass, and density of B. tectorum with sprayed or seed mixture applications did not differ between D7-treated and untreated areas at any time within the study (F1,6 ≤ 1.42; p ≥ 0.28). D7 as a seed mixture did not significantly impact densities of native seedlings (F1,6 = 1.27; p = 0.30) at any time during the study. Results contrasted with previous D7 studies that showed effective control of B. tectorum within three years of treatment. Since bioherbicidal methods are being commonly applied, we believe that reporting negative results are important for future meta-analytical studies that provide managers with information on the likelihood for weed suppressive bacteria to effectively control weeds.
|Title||Weed-suppressive bacteria applied as a spray or seed mixture did not control Bromus tectorum|
|Authors||David A. Pyke, Scott Shaff, Michael A Gregg, Julie L. Conley|
|Publication Subtype||Journal Article|
|Series Title||Rangeland Ecology and Management|
|Record Source||USGS Publications Warehouse|
|USGS Organization||Forest and Rangeland Ecosystem Science Center|