New Zealand Journal of Agricultural Research abstracts

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Invited paper

Pastoral weeds in New Zealand: status and potential solutions

G. W. Bourdôt¹

S. V. Fowler²

G. R. Edwards³

D. J. Kriticos⁴

J. M. Kean¹

A. Rahman⁵

A. J. Parsons⁶

¹AgResearch Ltd
Lincoln
Private Bag 4749
Christchurch 8140, New Zealand
graeme.bourdot@agresearch.co.nz

²Landcare Research
PO Box 69
Lincoln 7640, New Zealand

³Agricultural Science & Life Sciences Group
PO Box 84
Lincoln University
Lincoln 7647, New Zealand

⁴Ensis
Te Papa Tipu Innovation Park
Private Bag 3020
Rotorua 3046, New Zealand

⁵AgResearch Ltd
Ruakura Centre
Private Bag 3123
Hamilton 3240, New Zealand

⁶AgResearch Ltd
Grasslands Research Centre
Private Bag 11008
Palmerston North 4442, New Zealand

Abstract   Currently there are some 187 plant species, almost all exotic in origin, occurring as "weeds" in pastures in New Zealand. Judging from their occurrence in scientific papers published in the proceedings of the New Zealand Plant Protection Society, 65 of these species are, or have been considered historically, to be significant pastoral weeds. While 34 of these pastoral weeds are currently being managed under Regional Pest Management Strategies, 15 of these regionally managed species are apparently un-researched in New Zealand, implying that their management does not have a scientific basis. The aggregate cost of pastoral weeds to the New Zealand economy is estimated to be NZ$1.2 billion per annum, based on an analysis made in 1984, but this analysis is hampered by a lack of both objective data on the impacts of weeds on pastoral production and an accurate and comprehensive national census of the main problem species. Ongoing naturalisations, from an existing pool of exotic plant species estimated currently at 25 000, and new arrivals through international trade in plant species and germplasm, can be expected to steadily add to the list of pastoral weeds. Prioritisation of these weed species will be necessary if New Zealand's pastoral agricultural industries are to make long-term, economically optimal decisions about their management. Such prioritisation will require robust models of their current and potential distributions, their rates of population increase and spread, a full understanding of the merits and pitfalls of alternative control options, and robust models of their impacts on pastoral productivity.

Keywords   biological control; biosecurity; competition; economics; germplasm; herbicides; herbicide resistance; models; naturalisation; pastoral weeds; sleeper weeds; weed management

A06052; Online publication date 20 April 2007; Received 16 September 2006; accepted 27 February 2007

New Zealand Journal of Agricultural Research, 2007, Vol. 50: 139—161
0028—8233/07/5002—0139 © The Royal Society of New Zealand 2007

PDF file of entire paper: Print-quality (1243K) | screen-quality (667K)

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