Quantifying the economic cost of invertebrate pests to New Zealand’s pastoral industry

The invertebrate pests most commonly affecting New Zealand’s pastoral based production cause losses of up to $4.1B p.a. of which up to $1.6B occur on sheep and beef farms and $2.5B on dairy farms. The native scarab grass grub is the most costly pest causing losses of $940M on dairy farms and $693M on sheep and beef farms annually. The exotic scarab, black beetle, although only affecting approximately 1.1M ha, costs dairy farmers up to $918M and sheep and beef farmers up to $191M annually. Porina cause losses equating to $278M and $223M respectively. Pasture nematodes are estimated to cost up to $274M p.a. for dairy farmers and $326M p.a. for sheep and beef farmers. Two exotic pests, Argentine stem weevil ($62M p.a.) and clover root weevil ($193M p.a.), both subject to successful biocontrol management still cause considerable losses to farmers. The cost of biocontrol resistance in Argentine stem weevil is unknown but may be $100-160M. Lesser pests also contribute to lost production. However, the economic cost to New Zealand associated with them is difficult to calculate due to the variable nature of infestations on both temporal and spatial scales. At farm and paddock level it is abundantly clear that substantial savings could be made if pest management is achieved. It is equally clear that in many instances the tools to do so are limited but if developed would contribute substantially to farm profitability.