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United States Department of Agriculture

Agricultural Research Service

Research Project: BIOLOGY AND MANAGEMENT OF INVASIVE WEEDS IN THE WESTERN UNITED STATES

Location: Exotic and Invasive Weeds Research

Title: Integrated control and assessment of knapweed and cheatgrass on Department of Defense installations. 2007 Annual Report/Final Report SI-1145

Authors
item Paschke, Mark - COLORADO STATE UNIV.
item Redente, Edward - COLORADO STATE UNIV.
item Klein, Donald - COLORADO STATE UNIF.
item SMITH, LINCOLN

Submitted to: Government Publication/Report
Publication Type: Government Publication
Publication Acceptance Date: February 28, 2008
Publication Date: February 28, 2008
Citation: Paschke, M.W., Redente, E.F., Klein, D.A., Smith, L. 2008. Integrated control and assessment of knapweed and cheatgrass on Department of Defense installations. 2007 Annual Report/Final Report SI-1145. Government Publication/Report. 21 p.

Interpretive Summary: Spotted and diffuse knapweeds and cheatgrass 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 cheatgrass. 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 three military bases 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 field studies to control alien invasive weeds (cheatgrasses and knapweeds) at 3 military bases for 2 to 6 years. Four methods to accelerate natural plant succession were tested: 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 reduced availability of soil nitrogen and temporarily reduced biomass of winter annuals (mainly cheatgrass). 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. Insects were released at Ft. McCoy and plant populations have been monitored for 2 years.

Last Modified: 8/27/2014
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