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The study is the first to estimate the financial impact of invertebrate pests such as the grass grub, black beetle, nematodes and weevils in terms of lost productivity for pastoral farming.
Of the total estimated annual losses of between $1.7 billion and $2.3 billion, in "average" years up to $1.4 billion of losses occurred on dairy farms, and up to $900 million on sheep and beef farms.
"Our research shows that the impact of the grass grub alone costs dairy farms up to $380 million, and sheep and beef farms up to $205 million, each year," AgResearch scientist Colin Ferguson said.
Losses attributable to these pasture pests were usually determined either on the basis of the amount of foliage they consumed, or reductions in pasture production.
However, AgResearch’s study had used the reduction in pasture production to estimate the impact on milk production revenue for dairy farms, and on meat production revenue for sheep and beef farms.
"What this provides us is a good picture of the challenge we and farmers face with pasture pests, and it reinforces the need to invest in new and cost-effective ways to better control these pests," Mr Ferguson said.
"AgResearch is looking at pest control on a number of fronts, including the development of new biopesticides — naturally occurring organisms that can be used to target specific pest species, instead of chemical treatments that can be expensive and have unwanted impacts on the environment."
The study was initiated as part of Pastoral 21 Next Generation Dairy Systems and funded by DairyNZ, Fonterra, the Dairy Companies Association of New Zealand, Beef + Lamb New Zealand and the Ministry of Business, Innovation and Employment and has been completed with funding from AgResearch.