Spotted Knapweed, Centaurea Stoebe, Early Detection and Rapid Response in Alaska
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Spotted Knapweed, Centaurea stoebe, Early Detection and Rapid Response in Alaska Gino Graziano Division of Agriculture, Plant Materials Center [email protected] 907-745-8127 Project Funded by the USFWS, American Recovery and Reinvestment Act Summary Spotted knapweed, Centaurea stoebe, is targeted for eradication in Alaska because it presents a serious threat to natural and agricultural resources, and is present in few locations in Alaska. The enclosed report resulted from a 2 year project funded by the U.S. Fish and Wildlife Service (USFWS) through the American Recovery and Reinvestment Act (ARRA). Through this project each infestation of spotted knapweed was visited to confirm its continued presence or absence. The project implemented outreach advertisements through radio, the Milepost, and fliers distributed to passengers of the Alaska ferry system to foster public participation in prevention and early detection. We suggest prevention activities for land managers which include ensuring clean equipment is used if brought from sources outside Alaska. Habitat suitability was modeled from the presence of existing locations with the assistance of the U.S. Geological Survey (USGS). Finally, tasks to continue eradication and prevention efforts into the future are discussed. Introduction Spotted knapweed, Centaurea stoebe, is recorded as present or having occurred at 23 locations in Alaska. Of those original 23 locations only 5 infestations still persist. Infestations of such highly invasive plants are obvious high priorities for Early Detection and Rapid Response (EDRR) in Alaska. Spotted knapweed is a notorious invasive plant that has infested millions of acres in the Western United States, and parts of Canada. Knapweed ranks 86/100 according to the Invasive Plant Ranking System for Alaska (Carlson et al. 2008). The ranking applies to the Interior Boreal and Southcoastal ecoregions of Alaska. The arctic and alpine ecoregions are not predicted to be vulnerable to spotted knapweed invasion. Spotted knapweed is a biennial or short lived perennial with a showy purple flower that is shaped like an urn. For more information on identification see the description in “Invasive Plants of Alaska” (AKEPIC 2005) and Figure 1. Outside of Alaska knapweed is known to create dense stands that crowd out native and desirable plant species in both natural and farm ecosystems. The competitive advantages that spotted knapweed has over other species includes heavy seed production, 20,000 seeds or more (Royer and Dickinson 1999), and the use of allelopathy to inhibit competition of plants (Whitson et al. 2000). 1 Spotted knapweed along Turnagain arm Photo courtesy Michael Rasy, University of Alaska, bugwood.org. When knapweed takes over an area it forms thick stands often reducing native plant diversity, reducing forage quality in pastures and for wildlife. Winter-ranging elk, for example, are known to avoid knapweed infested areas (Rice et al 1997). Invaded areas of the Western United States, normally occupied by native bunch grasses, are known to have approximately three times as much sediment runoff as uninvaded areas (Rice et al. 1997). Increased erosion may present potential problems for water quality that could affect salmon and salmon habitat. Spotted knapweed arrives to new habitats primarily through interactions with humans. Suspected routes of human dispersal of knapweed include dispersal on vehicles, machinery and aircraft, contaminated products such as hay, commercial seed and floral arrangements (Mauer et al. 1987). Spotted knapweed eradication is an obvious priority for invasive plant management in Alaska. The combination of threat to resources, and limited number of known infestations lends to the possibility for eradication. Indeed eradication efforts for spotted knapweed in Alaska were already underway, however, the effort was inconsistent with little follow up and no coordination between agencies. The necessary stimulus for coordinating the eradication effort and increasing prevention efforts was provided by the American Recovery and Reinvestment Act. Spotted knapweed, Centaurea stoebe, has been recorded at 23 different locations in Alaska, all in the Southeast or Southcentral region (Figure 1). During the summer of 2009 all known C. stoebe infestations were inventoried and treated by removing all C. stoebe plant parts found. This effort sought to evaluate the status of current infestations and to begin a coordinated statewide eradication effort. 2 Field work performed during the summers of 2009 and 2010 provided information necessary for a thorough evaluation of C. stoebe populations in Alaska. The Alaska Exotic Plant Information Clearinghouse (AKEPIC, http://akweeds.uaa.alaska.edu), a statewide database of invasive plant occurrences and management efforts, currently lists 17 unique C. stoebe sites, but it has been found at 23 distinct locations in Alaska. In addition to the field work performed, research was conducted to compile a thorough history of each location. The geographical discontinuity of Alaskan C. stoebe infestations has led to inconsistent data collection, sharing, and control efforts. To better understand the C. stoebe inventory and management history all available site observation records were verified and original site observers were contacted for information that was previously not recorded in AKEPIC. These efforts have produced a more comprehensive understanding of C. stoebe infestations in Alaska, and are recorded here. Summer 2009-2010 Fieldwork: Inventory and Eradication 2009-2010 inventory and control efforts confirmed C. stoebe persists at 7 of the 23 recorded infestations in Alaska seven populations are widely distributed, with one in a remote region of Prince of Wales Island, one on Kupreanof Island near Kake, one near Haines, three along Turnagain Arm (near Anchorage), and one newly discovered site in Anchorage (Figure 1). The extent of all known populations is small, with none extending beyond 0.5 acres in size. A summary of 2009 and 2010 inventory and management efforts for the 23 known infestations is provided here and in Tables 1 and 2. What follows is a chronology of activities fore each infestation of spotted knapweed in Alaska. Turnagain Arm Five C. stoebe infestations are recorded along the Seward Highway and Alaska Railroad corridor which parallels Turnagain Arm, bearing southeast from Anchorage. All infestations are located along the stretch of highway between Beluga Point and Indian. The first of these sites was found in 2003 by Michael Shephard (United States Forest Service, USFS). Additional infestations were recorded in the following years, with the most recent, at Beluga Point, found in 2008 by Michael Rasy (University of Alaska Fairbanks Cooperative Extension Service, CES). These infestations were hand pulled at least once annually by CES staff and others since they were found. In 2009 and 2010 all Turnagain Arm sites were visited twice, surveyed with GPS equipment, and plants were hand-pulled when found. On June 22, 2009 Gino Graziano (DOA), Michael Rasy (CES), and Matt Keltzenberg (Alaska Railroad, ARR) surveyed all sites to evaluate the extent of the infestations. The surveys were conducted 200 meters along the highway or railroad surrounding each infestation. A visit was then conducted on June 23, 2009 by Gino Graziano (DOA), Michael Rasy (CES), Jeff Heys (United States Fish and Wildlife Service, USFWS), Rob Develice (USFS), and Matt Keltzenberg (ARR). C. stoebe 3 was found and pulled at 3 sites (Table 1 and 2) as follows: 54 plants at TURNAGAIN_01 (Beluga Point), 2 plants at TURNAGAIN_03 (Party World), and 16 plants at TURNAGAIN_04 (Falls Creek). No plants were found in surveys of TURNAGAIN_02 (Rainbow) and TURNAGAIN_05 (Indian). On September 10, 2009, Turnagain Arm sites were revisited by Andrew Weaver (DOA), Gino Graziano (DOA), Rob Develice (USFS), and an ARR employee. C. stoebe was again found at and removed from, Beluga Point (124 plants), Party World (20 plants), and Falls Creek (8 plants) (Table 2). No plants were found in surveys of the Rainbow and Indian sites. 2010 field work included two site visits, one on July 8th and the second September 16th. During these visits 87 (July) and 68 (September) stems were pulled at Beluga Point. 6 (July) and 8 (September) were found at Party world, and 4(July) and 0 (September) were found at the infestation near the Falls Creek trailhead. The other sites where infestations were previously recorded along Turnagain arm continue to have no regrowth of spotted knapweed. Knapweed management along Turnagain Arm Photos courtesy Jeff Heys USFWS 4 Latitude Longitude Location Notes Seward HWY, Beluga point between the roadside pullout and the railroad tracks around the West end of the parking area to 20 meters -149.69534 61.00724 west of the parking area Seward HWY, Across the seward highway from the Rainbow trailhead, in a very narrow roadside meadow just east of a pull-off on the S side of -149.6353681 60.99743602 the highway. Seward HWY, At climbing pullout South of Beluga point. Knapweed located on South side of the highway between the guard rail and the -149.61996 60.99062 tracks, but up on the bluff above the tracks. Seward HWY, Near the Falls Creek trailhead below retaining wall on South side of highway about 100 m. east of the trailhead, next to the RR -149.57289 60.98428 tracks. 5 Valdez Four C. stoebe infestations are recorded in AKEPIC for the Valdez area. All sites are found adjacent to a one mile stretch of the Richardson Highway located 3-4 miles East of Valdez. Here the highway skirts a large estuary, very near the location of the grain silos. Sites near Valdez were originally recorded by Michael Shephard (USFS) and Cynthia Snyder (USFS) on Aug. 11, 2004. In 2009 all four sites were visited twice, on July 08 by Gino Graziano (DNR-PMC) and Trish Wurtz (USFS) and on August 09 by Andrew Weaver (DNR-PMC). Sites were located using GPS equipment and the roadsides were surveyed for 100 meters from the location of the reported infestations in each direction. No knapweed was found during these surveys (Table 1).