Proceedings of the Third International Conference on Invasive ...

<strong>Proceedings</strong> <strong>of</strong> <strong>the</strong> <strong>Third</strong> <strong>International</strong> <strong>Conference</strong> on Invasive SpartinaChapter 4: Spartina Control and ManagementCOMPARISON OF CHEMICAL AND MECHANICAL CONTROL EFFORTS FOR INVASIVESPARTINA IN WILLAPA BAY,WASHINGTONK. PATTENWashington State University Long Beach Research and Extension Unit, 2907 Pioneer Road, Long Beach, WA 98631;pattenk@wsu.eduWillapa Bay, Washington, hosts <strong>the</strong> largest invasive Spartina population in North America. Stateand federal agencies have been conducting large-scale mechanical and chemical control efforts on<strong>the</strong> affected lands during <strong>the</strong> past decade with varying degrees <strong>of</strong> success. Assessments <strong>of</strong> <strong>the</strong> longtermefficacy, cost effectiveness and ecological risk <strong>of</strong> <strong>the</strong> various control tools are presented. Nolong-term control was achieved with multiple years <strong>of</strong> disking. Crushing Spartina was onlysuccessful when <strong>the</strong> plant was driven well below <strong>the</strong> surface sediment. This occurred on s<strong>of</strong>tsediment and a thin root mat. Winter tilling provided good control, but spring and summer tillingonly marginal control. In sites where seed stalks were tilled into <strong>the</strong> sediment during <strong>the</strong> winter,<strong>the</strong>re was a solid stand <strong>of</strong> seedlings <strong>the</strong> following spring. Spartina control with glyphosate at <strong>the</strong>high hand-sprayed rates (5–8% v/v) averaged approximately 50%, with permanent control takingseveral years <strong>of</strong> re-treatment. Control from late season (September/October) hand-sprayedglyphosate was poor. Control with broadcast application <strong>of</strong> glyphosate (8.4 kilograms activeingredient per hectare (kg ai/ha)) was highly variable. Although brown-down was usually observed,<strong>the</strong>re was no permanent control except under ideal conditions (clean leaves, clean spray water andseveral days <strong>of</strong> dry time), in which case up to 74% control was achieved. Based on same seasonobservations, large-scale control appears promising using broadcast (aerial and ground) and handsprayedimazapyr. Most variability with imazapyr occurred when hand-sprayed applications failedto achieve good canopy coverage. Best control, lowest long-term cost and least ecological riskoccurred with broadcast imazapyr application in June.Keywords: glyphosate, imazapyr, tilling, crushing, modeling, eradication, SpartinaINTRODUCTIONResearch to develop better control methods for invasiveSpartina has been on-going on a global scale for many years(Frid et al. 1999; Garnett et al. 1992; Kilbride et al. 1995;Major et al. 2003; Patten 2002; Patten and Stenvall 2002;Pritchards 1995; Shaw et al. 1995). How well <strong>the</strong>se variousmethods work when implemented by large-scale controlprograms has been poorly documented. In addition, <strong>the</strong>re islittle information about how successful <strong>the</strong>se programs are inachieving <strong>the</strong>ir control or eradication goals.Willapa Bay, Washington State, USA currently hostsone <strong>of</strong> <strong>the</strong> largest Spartina alterniflora infestations in <strong>the</strong>world. In 1993 <strong>the</strong> state legislators unanimously passed <strong>the</strong>Revised Code <strong>of</strong> Washington 17.26 which mandates thatSpartina shall be eradicated. To accomplish this goal, <strong>the</strong>rehave been large-scale control efforts on Spartina in WillapaBay since 1995. Those efforts have included an array <strong>of</strong>mechanical and chemical practices implemented by state,federal and private stakeholders. Treating Spartina,however, has not led to eradication. Control has not comeclose to keeping pace with <strong>the</strong> 15 to 20% annual rate <strong>of</strong>spread (Hedge et al. 2002), despite state and federal agencyexpenditures <strong>of</strong> $500,000-$1 million to treat thousands <strong>of</strong>acres <strong>of</strong> Spartina per year (WSDA 1999 to 2003). Asuccessful eradication strategy requires that <strong>the</strong> specificcontrol practices being utilized have adequate efficacy toaccomplish <strong>the</strong> task. Unfortunately, according to a study by<strong>the</strong> Government Accounting Office (GAO 2002), mostinvasive species management programs fail to objectivelyassess, improve and realign <strong>the</strong>ir control strategies torealistically correspond to <strong>the</strong>ir eradication goals. TheSpartina control effort in Willapa Bay is no exception to thisfailure <strong>of</strong> management strategies (Hedge et al. 2002).The objectives <strong>of</strong> this study were to monitor andevaluate <strong>the</strong> most commonly used Spartina control efforts inWillapa Bay and to determine if <strong>the</strong> efficacy <strong>of</strong> those effortsis sufficient to allow state and federal agencies toaccomplish <strong>the</strong>ir eradication goals.MATERIALS AND METHODSMajor mechanical and chemical control effortsconducted by Washington State Department <strong>of</strong> Agriculture(WSDA), Washington State Department <strong>of</strong> Fish andWildlife (WDFW), Washington State Department <strong>of</strong> NaturalResources (WDNR), Willapa National Wildlife Refuge(WNWR) and private tideland owners in Willapa Bay from2001 to 2004 were identified and selected for evaluation.- 249 -