Proceedings of the Third International Conference on Invasive ...

Chapter 4: Spartina Control and Management<strong>Proceedings</strong> <strong>of</strong> <strong>the</strong> <strong>Third</strong> <strong>International</strong> <strong>Conference</strong> on Invasive Spartinato 1998 that have shown promise at o<strong>the</strong>r sites, includingcovering with heavy-duty landscape fabric, repeatedmowing, artificial inundation and removal by manualdigging.Results <strong>of</strong> <strong>the</strong>se tests indicated that covering <strong>the</strong>Spartina with landscaping fabric (Mirafi 500 or Amoco2002) anchored by gutter spikes pushed into <strong>the</strong> sedimentwas <strong>the</strong> most effective and least environmentally detrimentalmethod, <strong>of</strong> those that were tried, for controlling this invasivespecies at Cox Island. Leaving <strong>the</strong> fabric on for two yearseffectively kills <strong>the</strong> Spartina, leaving behind bare ground.After removal <strong>of</strong> <strong>the</strong> fabric, native salt-marsh vegetation recolonizes<strong>the</strong>se bare patches on its own so active planting <strong>of</strong>native vegetation is not necessary.The landscaping fabric we use (Amoco 2002) is a tough,woven black plastic fabric (geotextile) that resists UV lightand holds up well in a saltwater environment. We havesuccessfully used pieces <strong>of</strong> this fabric for six consecutiveyears (on three different patches for two years each) before itbecame too thin to block light. Since <strong>the</strong> fabric is woven, cutedges need to be folded under so <strong>the</strong> wind does not unravel<strong>the</strong> edges. This fabric is available from ACF West Inc. inPortland, Oregon (1-800-878-5115 or 503-771-5115). Itscost ranged from $315/roll (picked up) to $385/roll (locallydelivered). These rolls contain 6,300 square feet (ft 2) <strong>of</strong>fabric and measure 18 ft x 350 ft.To install <strong>the</strong> fabric, we identify <strong>the</strong> spatial limits <strong>of</strong> <strong>the</strong>patch, mow <strong>the</strong> vegetation around <strong>the</strong> boundary <strong>of</strong> <strong>the</strong> patchso <strong>the</strong> fabric lays flat, cut a piece <strong>of</strong> fabric <strong>of</strong> sufficient sizeto extend well beyond <strong>the</strong> border <strong>of</strong> <strong>the</strong> patch, and pin inplace with gutter spikes every two to three feet along <strong>the</strong>edges while pulling <strong>the</strong> fabric taut. The fabric should extenda minimum <strong>of</strong> two feet beyond <strong>the</strong> edge <strong>of</strong> patches to helpprevent any rhizomes from growing out beyond <strong>the</strong>covering. We fold <strong>the</strong> edge <strong>of</strong> <strong>the</strong> fabric under and push aspike with a washer (to keep <strong>the</strong> head <strong>of</strong> <strong>the</strong> spike fromgoing through <strong>the</strong> fabric) through <strong>the</strong> fabric and pound itinto <strong>the</strong> substrate. If <strong>the</strong> ground is too s<strong>of</strong>t in places to get agood grip with <strong>the</strong> gutter spikes, we use nine-inch nailsinstead. (These also tend to last longer in <strong>the</strong> saltwaterenvironment and do not need washers.). We angle <strong>the</strong> spikestoward <strong>the</strong> center <strong>of</strong> <strong>the</strong> covering as we drive <strong>the</strong>m in to helpprevent <strong>the</strong> tidal currents and wind from pulling up on <strong>the</strong>edges. If additional anchoring is needed, for example wheretwo pieces <strong>of</strong> fabric overlap, two spikes can be driven in atopposite angles in <strong>the</strong> same spot.In <strong>the</strong> fall <strong>of</strong> 1998, we began efforts to control <strong>the</strong> smalloutlier patches <strong>of</strong> Spartina before <strong>the</strong>y could turn into largepatches. This strategy <strong>of</strong> beginning with small outliers hasproven to be <strong>the</strong> most effective way to contain a non-nativespecies invasion (Moody and Mack 1988). As <strong>of</strong> 2004, wehave controlled all <strong>of</strong> <strong>the</strong> outliers and are making progresson <strong>the</strong> main infestation area. The Spartina in this area hasgrown from three patches in 1939 to a Spartina meadowtoday. We are covering <strong>the</strong> perimeters <strong>of</strong> <strong>the</strong>se meadows tohalt <strong>the</strong>ir spread and will work towards <strong>the</strong>ir interiors insuccessive years. Each year we mow flowering patches thathave not yet been covered to prevent seed set. The patchesare mowed from mid- to late-August with gas-poweredstring trimmers and are cut well above <strong>the</strong> ground surface toavoid tearing out rhizomes that might spread <strong>the</strong> infestation.Overall, we have successfully restored about 0.81 ha (2ac) <strong>of</strong> former Spartina patches to native salt marsh. At leastano<strong>the</strong>r 1.62 ha (4 ac) are currently covered with fabric. Weestimate that 0.43 ha (1.1 ac) <strong>of</strong> large Spartina patchesremain uncontrolled on <strong>the</strong> island, which we hope to coverby <strong>the</strong> end <strong>of</strong> 2005. Controlling this invasive species on CoxIsland will not only restore native salt marsh to <strong>the</strong> island,but will also help to prevent Spartina's spread to o<strong>the</strong>r parts<strong>of</strong> <strong>the</strong> Siuslaw Estuary and to o<strong>the</strong>r estuaries in Oregon andWashington.I believe this weed control method shows promise foruse on o<strong>the</strong>r invasive species as well (we are currently tryingit on upland grasses and reed canarygrass [Phalarisarundinacea]). While it may not be practical for wellestablished invasive species populations that cover morethan 4-8 ha (~10-20 ac), it is a viable non-chemical controlmethod for outlier patches and small pioneering infestationson a site.ACKNOWLEDGEMENTSWe are very grateful to <strong>the</strong> following for providingfunding for this project: NOAA/TNC Community-basedRestoration Program; Oregon Watershed EnhancementBoard; Oregon Department <strong>of</strong> Agriculture's Oregon StateWeed Board, Noxious Weed Control Grant Program; andU.S. Fish and Wildlife Service, North American WetlandsConservation Act, Small Grants Program.REFERENCESAberle, B.L. 1993. The biology and control <strong>of</strong> introduced Spartina(cordgrass) worldwide and recommendations for its control inWashington. Master's Thesis, Olympia, WA: The EvergreenState College.Daehler, C.C. and D.R. Strong. 1996. Status, prediction, and prevention<strong>of</strong> introduced cordgrass Spartina spp. invasions in Pacificestuaries, USA. Biological Conservation 78:51-58.Frenkel, R.E. and T.R. Boss. 1988. Introduction, establishment andspread <strong>of</strong> Spartina patens on Cox Island, Siuslaw Estuary, Oregon.Wetlands 8:33-49.Moody, M.E. and R.N. Mack. 1988. Controlling <strong>the</strong> spread <strong>of</strong> plantinvasions: <strong>the</strong> importance <strong>of</strong> nascent foci. Journal <strong>of</strong> AppliedEcology 25:1009-1021.Pfauth, M., M. Sytsma, and D. Isaacson. 2003. Oregon SpartinaResponse Plan. Portland State University, Center for Lakes andReservoirs report prepared for Oregon Department <strong>of</strong> Agriculture.- 264 -