Dairy production revenue losses in New Zealand due to giant buttercup (Ranunculus acris)

Giant buttercup (Ranunculus acris L.), a species of European origin, is widespread throughout New Zealand, and is an intractable weed of dairy pastures in parts of the south Auckland, Hawke's Bay, and Taranaki regions and in the districts of Southern Wairarapa, Horowhenua, and Tasman. In this study, the seasonal progression of the weed's ground cover in dairy pastures in the Tasman District was measured during 1989-90 and used, in conjunction with monthly weed-free pasture dry matter production values, to estimate the annual percentage loss in pasture production due to a typical infestation of the weed subjected to typical control measures. Extrapolation to other infested regions and districts provided a national estimate of milk solids revenue loss due to giant buttercup in New Zealand dairy pastures of $156 million in the 2001-02 season.