ARS | Publication request: Integrated Control and Assessment of Knapweed and Cheatgrass on Department of Defense Installations

Submitted to: Government Publication/Report
Publication Type: Government Publication
Publication Acceptance Date: January 30, 2005
Publication Date: January 30, 2005
Citation: Paschke, M.W., Redente, E.F., Warren, S.D., Klein, D.A., Smith, L., Klawitter, A.L., Mclendon, T. 2005. Integrated control and assessment of knapweed and cheatgrass on department of defense installations. 87 pp. (Government Publication)

Interpretive Summary: Spotted and diffuse knapweeds and cheat grass are important invasive alien weeds in rangelands of the western U.S. Although herbicides can provide effective, short term control of these weeds, they are not economical or environmentally acceptable to use over large areas. Insect biological control agents have been introduced for the two knapweeds, and carefully timed controlled burning has been used to help manage cheat grass. Integrating these primary management strategies with other vegetation management tools may help speed up the restoration of weedy sites to desirable rangeland vegetation. We conducted field experiments at two military bases during four years to evaluate the efficacy and synergy of four vegetation management tools: 1) reducing the weed population using biological control or burning, 2) reducing soil nitrogen availability using sugar, 3) seeding desirable plant species, and 4) inoculating native soil microbes. Biological control agents in combination with a drought reduced knapweed populations to extremely low densities at both locations. Remote sensing from helicopter was not sensitive enough to measure densities of either diffuse knapweed or cheatgrass at the field sites. A computer simulation model predicted sustained control of knapweeds at both locations and of Japanese brome at the Colorado site.

Technical Abstract: We conducted a 4-year study at 2 military bases to control non-indigenous invasive plant species (cheatgrasses and knapweeds) by using a combination of four manipulations to accelerate natural plant succession. These were: 1) reducing the target weed population using biological control or burning, 2) reducing soil nitrogen availability, 3) reseeding with desirable plant species, and 4) reintroducing the native late-seral soil microbial community. Increases in populations of insect biological control agents and a 2-year drought reduced spotted knapweed populations to extremely low levels at Ft. Carson, CO. Densities of diffuse knapweed decreased at Yakima Training Center, WA in the presence of high densities of biological control agents. Application of granular sugar (sucrose) reduced availability of soil nitrogen and temporarily reduced biomass of winter annuals (mainly Bromus species). Possible effects of the other treatments were not very evident. Aircraft collection of high-spatial resolution multispectral data was able to detect sucrose effects on vegetation composition, but was not able to specifically measure either diffuse knapweed or cheatgrass at the observed field densities. Computer simulation runs of the EDYS model predicted sustained control of knapweeds at both locations and of Japanese brome at the Colorado site.