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

30000

Wild

3000

Pest

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!