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Weed risk assessment and control Peter Williams, Mark Lewis, Alan Hastings, Rua Murray, Miranda Bennett, Jeff Diez, Ian Westbrooke, Rohan, Tanya Soboleva, Kyoko Fukuda, Ben Perdriau Risk assessment • Legally introduced species are assessed for “weediness” before being allowed into NZ • Some accidentally/illegally introduced • Many already present • Would like a method for quick assessment of weeds already introduced • Need info on cases of good plants turned bad Control • Control effort focussed on relatively small number of invasive species • RCs reluctant to add new species to strategy • But what about currently introduced (30000) and naturalised (3000) species that may be future pests? Introduced Wild Pest 30000 3000 300 • 3 categories of exotic species • Transition between categories • Limited control effort • Optimisation problem for allocation of control effort • Minimise present cost over finite time horizon • Linear -> “All eggs in one basket” • Nonlinear?? Pests can be divided into further categories • Different species (or class of species) • Different regions • RC categories: total control (eradication), surveillance (banned from sale), containment. Still to do… • Data on cost/damage of having species in each category • Include amount of spead? • Risk of transition between classes? • Maximum (and minimum?) effort for each class (or more realistic nonlinear control efficacy)? • Solve it!
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