ASSESSMENT OF SCOTCH BROOM (CYTISUS SCOPARIUS) DISTRIBUTION, DENSITY AND BIOLOGICAL CONTROL POTENTIAL ON FORT LEWIS

Goals / Objectives
1) Aerial assessment of Scotch broom populations. 2) Ground verification of Scotch broom density and distribution including seedbed characterization. 3) Population density and distribution assessment of the seed weevil, Exapion fuscirostre on Fort Lewis.

Project Methods
Aerial photograph and hyperspectral imagery will be collected and analyzed to provide a basemap of Scotch broom infested areas across several ranges at Fort Lewis. GIS-based maps will be developed and applied to estimate the population density and distribution of this invasive plant species. These maps will then be field validated using ground-based sampling. A random selection process will allow individual plants to be marked and measured in the field. Key plant attributes will be assessed including plant height, width, seedback status, plant phenological stage and amount of flower/ seedbud production. In parallel with ground-based assessments of plant characteristics, seed pod collections and dissections will allow beetle numbers to be assessed and their impact determined in terms of proportion damaged seed across a range of conditions. Documents Reimbursable with US Army Corps. Log 29310.

Progress 07/01/05 to 06/30/10

Outputs
Progress Report 4d Progress report. This report documents research conducted under a Reimbursable Agreement between ARS and the Army Corps of Engineers. Additional details of the research can be found in the report for the parent project 5325-22000-020- 00D, Biology and Management of Invasive Weeds in the Western US. Fort Lewis, located near Tacoma, WA, is one of the US Armys largest Strike Force Training Centers in the Western United States. It is also a significant training center for airborne troops and artillery/ gunnery range training. Several of its training ranges are highly infested with the exotic invasive shrub, Scotch broom (Cytisus scoparius) that the military has determined is detrimental to its training mission. It both limits the available training area and increases fire hazard where live shelling occurs on the base. It further degrades the natural environment by out competing native species for resources and thus reduces biodiversity. At the request of the US Army and associated Nature Conservancy land managers that assist the Army in range management, scientists from the USDA-ARS Exotic and Invasive Weed Research Unit in Albany, CA have begun a multi-year effort to assess the broom infestation, determine biological control impacts of a previously released seed feeding natural enemy (an Apion weevil), and to determine if other natural enemies of European origin hold potential for Scotch broom control. To date, different broom management strategies have been evaluated and compared for their impact on the biological control agents. Although some differences in population levels were detected in FY 2005, this effort is being repeated during the summer of 2006 to determine if the trends are repeatable. Additionally, a new insect natural enemy, a defoliating leaf beetle, was located in France and investigations are now underway to determine if this agent can be successfully used to help control Scotch broom. If successful, this technology would help management this invasive weed problem not only on Fort Lewis but throughout the Pacific Northwest where it is a continuing and spreading problem.

Impacts
(N/A)

Publications