The impact of invasive invertebrate pests in pastoral agriculture: a review

Non-indigenous, invasive invertebrate pests have a detrimental effect on the New Zealand economy through impacts on pasture and forage production. Estimates of the economic impact have varied from $800 million to $2 billion. This paper reviews the literature on plant biosecurity concerns in New Zealand, and examines five of the major invasive pests in pastoral agriculture: clover root weevil (Sitona lepidus Gyllenhal). Argentine stem weevil (Listronotus bonariensis Kuschel), lucerne weevil (Sitona discoideus Gyllenhal), and the lucerne aphids (Acyrthosiphon kondoi Shinji and Macrosiphum pisi Shinji). The difficulties in assessing risk impact, and the limited value of extrapolation from results from other countries are discussed, as is the potential for using computer models in assessing potential impact. Recommendations for research approaches for the future are made.