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 Managementto address aquatic herbicides. The revisions were adopted inJune <strong>of</strong> 2004, enabling ISP partners to issue Notices <strong>of</strong> Intent(NOIs) to be covered under <strong>the</strong> Statewide GeneralNPDES Permit for Aquatic Weed Control.The NPDES permit also requires developing an AquaticPesticide Application Plan (APAP) identifying <strong>the</strong> proceduresfor applying herbicides, <strong>the</strong> chemicals to be used, <strong>the</strong>species targeted for treatment, a description <strong>of</strong> <strong>the</strong> waterbodysystem, and o<strong>the</strong>r related information. Within <strong>the</strong> APAP is aWater Quality Monitoring Plan (WQMP), which defines <strong>the</strong>protocols for water quality sampling <strong>of</strong> treatment areaswhere herbicide is used. While <strong>the</strong> ISP developed <strong>the</strong> APAPon behalf <strong>of</strong> <strong>the</strong> ISP partners, <strong>the</strong>y contracted <strong>the</strong> services <strong>of</strong><strong>the</strong> San Francisco Estuary Institute (SFEI) to fur<strong>the</strong>r developand implement <strong>the</strong> WQMP for <strong>the</strong> work proposed by <strong>the</strong> ISPand its partners, and to report on its findings following <strong>the</strong>2004 treatment season (California Coastal Conservancy2004(c)).In addition, access permits from regional and localagencies were necessary for treatment on many <strong>of</strong> <strong>the</strong> 16sites slated for Spartina control and <strong>the</strong> ISP coordinated <strong>the</strong>irprocurement.TREATMENT METHODSA variety <strong>of</strong> methods can be used to treat non-nativeSpartina populations in <strong>the</strong> estuary. However, very rarely isany particular treatment method appropriate for all situations.In <strong>the</strong> FEIS/R, <strong>the</strong> ISP proposed a suite <strong>of</strong> controlmethods and approaches based on <strong>the</strong> cumulative expertise<strong>of</strong> Spartina control operations worldwide, especially <strong>the</strong>work being done to control S. alterniflora in Willapa Bay,Washington State, USA. In 2004, <strong>the</strong> ISP tested several possiblecontrol techniques to determine <strong>the</strong> relative benefits <strong>of</strong>each.Chemical ControlGlyphosate herbicide (Aquamaster® or Rodeo®) wasused in most <strong>of</strong> <strong>the</strong> area <strong>of</strong> Spartina infestation that waschemically treated in 2004. The application <strong>of</strong> herbicidescomprised <strong>the</strong> largest part <strong>of</strong> <strong>the</strong> Control Program for a host<strong>of</strong> reasons, not least <strong>of</strong> which was <strong>the</strong> need to control largeacreage at low cost to stay ahead <strong>of</strong> <strong>the</strong> rapid expansion rate<strong>of</strong> <strong>the</strong> invader. Moreover, this method has a relatively lowimpact on <strong>the</strong> treated marshlands in contrast to o<strong>the</strong>r treatmentoptions. Drawbacks to herbicide use include <strong>the</strong> potentialfor herbicide or fuel spills, negative public perception,timing restrictions, and potential water quality impacts. Glyphosateherbicide was applied via tracked amphibious vehicles(Hydrotraxx or Argo) fitted with spray apparatus, truckmountedspray equipment, backpack sprayers, shallowbottomedboats with outboard motors and broadcast aerialapplications via helicopter with a 30-foot boom fitted with anozzle array.Manual ControlFor those sites not yet fully established—where <strong>the</strong>rewere very small, pioneering infestations to be treated—manual control techniques were used. These methods were<strong>of</strong>ten incorporated into public outreach efforts, involvingvolunteer groups that worked on marshland restorationprojects. For smaller sites, digging <strong>the</strong> plants resulted ingood control, but swiftly exhausted worker enthusiasm andresulted in heavy impacts to <strong>the</strong> marsh. Digging plants ininfestations much larger than 25 square meters is prohibitivelyexpensive and has <strong>the</strong> potential to leave lasting damageto <strong>the</strong> treated marsh in <strong>the</strong> form <strong>of</strong> deep holes ortrenches. In such cases, tarping or covering <strong>of</strong> <strong>the</strong> plants wasused to good effect. Heavy syn<strong>the</strong>tic tarps were staked inplace over trampled stands <strong>of</strong> non-native Spartina in severallocations in <strong>the</strong> estuary, as well as at Point Reyes NationalSeashore on <strong>the</strong> outer coast north <strong>of</strong> <strong>the</strong> Golden Gate. Tarpswere left in place for at least eight months and required regularmonitoring to assure that <strong>the</strong> covering remained in placeduring tidal fluctuation, especially storms. Removal <strong>of</strong> <strong>the</strong>covering following successful control <strong>of</strong> <strong>the</strong> Spartina was<strong>of</strong>ten difficult because <strong>of</strong> <strong>the</strong> heavy accumulation <strong>of</strong> mud ontop <strong>of</strong> <strong>the</strong> tarps, requiring laborious excavations to unearth<strong>the</strong> covering. Drawbacks to covering include <strong>the</strong> high cost <strong>of</strong>installation, maintenance and removal and <strong>the</strong> attendantdamage to <strong>the</strong> marsh, as well as <strong>the</strong> negative environmentalimpacts <strong>of</strong> petrochemical production associated with <strong>the</strong>manufacture <strong>of</strong> <strong>the</strong> heavy syn<strong>the</strong>tic fabric used in this treatmentmethod. Two <strong>of</strong> <strong>the</strong> sub-areas identified for Spartinacontrol in 2004 used small-scale mowing <strong>of</strong> <strong>the</strong> infestation.Gas-powered hand mowers fitted with a tri-blade were ableto make quick work <strong>of</strong> <strong>the</strong> standing material which was ei<strong>the</strong>rleft in place in <strong>the</strong> marsh (early season, pre-seed set) orremoved from <strong>the</strong> marsh and disposed <strong>of</strong> at a landfill (lateseason, post seed-set). Mowing in this way serves to controlseed and pollen spread and may slow <strong>the</strong> vegetative expansion<strong>of</strong> <strong>the</strong> Spartina clone by usurping root reserves. Mowingalone does not kill <strong>the</strong> plants, however. Unless coupledwith o<strong>the</strong>r control methods, mowing would need to be implementedseveral times each year in perpetuity and yetwould still allow some vegetative expansion.O<strong>the</strong>r methods <strong>of</strong> Spartina control tried elsewhere werenot attempted in <strong>the</strong> 2004 control season for various reasons.Macerating or tilling was not used because <strong>of</strong> <strong>the</strong> concerns<strong>of</strong> land managers that <strong>the</strong> high amount <strong>of</strong> urban refuse presentin estuary marshes (tires, shopping carts, blocks <strong>of</strong> concrete,pieces <strong>of</strong> metal, wood debris embedded with bolts ornails) and natural wrack (driftwood logs), would result inhigh maintenance costs or operator injury. The extremelys<strong>of</strong>t nature <strong>of</strong> most <strong>of</strong> <strong>the</strong> estuary mud where control wouldtake place was also taken into consideration, as <strong>the</strong> machineryinvolved in <strong>the</strong>se methods is heavy and very likely to getstuck in place. Crushing <strong>the</strong> plants, where machinery is used- 219 -