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 ManagementFusilade to control rice grass (Davies 1999). This assessmentfound that although <strong>the</strong> available information was limited,<strong>the</strong> use <strong>of</strong> Fusilade to control rice grass represents a lowenvironmental risk. The report also contained a range <strong>of</strong>recommendations that DPIWE <strong>the</strong>n used to refine itsmanagement program (e.g. initially limiting spray events to0.5 hectares per day as a precautionary approach in view <strong>of</strong>limited available information), design an environmentalmonitoring program, and target future research.The risk assessment recommended that fur<strong>the</strong>r studiesbe conducted to better understand <strong>the</strong> potential effects <strong>of</strong>Fusilade on Crassostrea gigas. Laboratory-based researchwas conducted, in collaboration with <strong>the</strong> Pacific oysteraquaculture industry, to investigate <strong>the</strong> potential effects <strong>of</strong>Fusilade on survival and development <strong>of</strong> C. gigas (Hedge etal. 1999). The investigation also included a laboratory/fieldcomponent that examined ingestion and depuration <strong>of</strong> <strong>the</strong>Fusilade active ingredient (fluazifop-P-butyl) and its primarydegradation product (flauzifop-P) in C. gigas when exposedto expected field concentrations. The findings <strong>of</strong> <strong>the</strong>investigation provided fur<strong>the</strong>r evidence that Fusiladepresented a low environmental risk and was also animportant factor in securing <strong>the</strong> support <strong>of</strong> <strong>the</strong> Pacific oysteraquaculture industry for <strong>the</strong> management program.In 1999, an environmental monitoring program wasdesigned to include <strong>the</strong> following components:• Water quality monitoring to assess fluazifop-P butyl andfluazifop-P concentrations at a variety <strong>of</strong> locations ineach estuary during and following initial controloperations;• Shellfish sampling to monitor ingestions <strong>of</strong> fluazifop-Pbutyl in C. gigas;• Small-scale, comprehensively designed biomonitoringprogram <strong>of</strong> benthic macroinvertebrates in areas sprayed;and• Mapping <strong>the</strong> location and size <strong>of</strong> rice grass infestationsfollowing treatments with Fusilade.Collectively, results from research on C. gigas and <strong>the</strong>environmental monitoring program provided additionalassurance <strong>of</strong> environmental safety; consequently <strong>the</strong>management program increased <strong>the</strong> use <strong>of</strong> Fusilade to allowtreatment <strong>of</strong> up to one hectare per day.More recently, two research projects are underway toinvestigate <strong>the</strong> impact <strong>of</strong> rice grass removal on benthiccommunities in <strong>the</strong> Rubicon/Port Sorell estuary and <strong>the</strong>potential effects <strong>of</strong> <strong>the</strong> release <strong>of</strong> sediments resulting fromlarge-scale rice grass removal in <strong>the</strong> Tamar River. Theseprojects will provide useful information to decision makerswhen reviewing management objectives for <strong>the</strong> tworemaining large infestations (i.e. Rubicon/Port Sorell andTamar River).Reduction <strong>of</strong> infestationsThe Management Strategy provided clear direction forprioritizing <strong>the</strong> reduction <strong>of</strong> infestations. The generalapproach was to focus on <strong>the</strong> smallest infestations (i.e.Derwent River, St Helens, Little Swanport estuary andBridport infestations) progressively building up to largerinfestations (i.e. Circular Head, Rubicon/Port Sorell andTamar River). A small, multi-disciplinary management teamwas used to reduce all targeted infestations to <strong>the</strong> pointwhere <strong>the</strong> efforts <strong>of</strong> local communities and industry becameimportant for locating remnant patches or isolated plants.Area-based Management Plans contained <strong>the</strong> specific details<strong>of</strong> how each infestation would be reduced (i.e. managementobjectives and responsibilities, control techniques andcontrol period). This was an important planning tool thatwas used to synchronize <strong>the</strong> efforts <strong>of</strong> <strong>the</strong> DPIWE, localcommunities and industry.The management team consisted <strong>of</strong> a core <strong>of</strong> threepeople, one management <strong>of</strong>ficer and two technical <strong>of</strong>ficers.A hovercraft and operator were contracted and <strong>the</strong> vesselfitted with a 50-liter spray tank, low spray equipment and100-meter remote-controlled, retractable hose. O<strong>the</strong>requipment used included all terrain vehicles fitted with lowpressurespray equipment and backpack low-pressure sprayunits. The primary control technique was application <strong>of</strong>Fusilade (application rate <strong>of</strong> 1000 litres/hectare <strong>of</strong> 1%Fusilade solution mixed with freshwater and <strong>the</strong> surfactantBS1000 at 0.2% vol/vol to maximize efficiency). A review<strong>of</strong> field-work data sheets showed <strong>the</strong> management teamtypically achieved efficacies <strong>of</strong> 90-99%. In 2002, <strong>the</strong>DPIWE decided to engage commercial weed managementcontractors to assist with treatment in <strong>the</strong> Circular Headregion. A comparison <strong>of</strong> costs and efficacies between <strong>the</strong>management team and commercial weed contractors isprovided in Table 2.Table 3 provides a summary <strong>of</strong> <strong>the</strong> infestations, <strong>the</strong>ircurrent management objectives and size in 2002 relative to1997. The area <strong>of</strong> infestation at Derwent River, St Helens,Little Swanport estuary and Bridport have all been reducedby 99% and are on target for achieving <strong>the</strong> managementobjective. The Circular Head infestation has been reduced byapproximately 50% and is also on target to achieve <strong>the</strong>management objective. The Rubicon/Port Sorell infestation,although having increased in total area, has beensuccessfully confined to <strong>the</strong> upper half <strong>of</strong> <strong>the</strong> estuary. TheTamar River infestation, <strong>the</strong> largest in Tasmania, appears tohave increased its area but is thought to be confined to <strong>the</strong>Table 2: Comparison <strong>of</strong> costs and efficacies between <strong>the</strong> management teamand commercial weed contractors for <strong>the</strong> application <strong>of</strong> Fusilade in <strong>the</strong>Circular Head region in 2002 (estimate <strong>of</strong> costs provided by DPIWE).Control CrewManagementTeamAveragearea treated(ha./day)Efficacy(%)CostUS $/ha0.5 ~95 2,500Contractors 1.0 >90 1,120- 245 -