An app to assist farmers to control the pasture weed species giant buttercup has been developed by AgResearch and is available free to use from the Dairy NZ website.   

Dr Graeme Bourdȏt, AgResearch principal scientist, Weeds, Pests and Biosecurity Team, says the app enables the user to determine if the giant buttercup infestation in a paddock is economically worthwhile controlling (do the benefits outweigh the costs?).

“It accounts for the loss of clovers from herbicide damage, enables herbicide options to be compared and herbicide resistance to be managed.”

The tool requires estimates for:

  • % of the pasture covered by the buttercup prior to the intended control operation
  • pasture drymatter eaten or grown currently in the paddock
  • conversion rate for pasture drymatter to milksolids
  • pasture utilisation rate
  • clover content
  • milksolids payout
  • herbicide cost
  • N-fertiliser cost and % N content
  • herd lactation length
  • stocking rate

Default values which can be edited are provided as examples for some of these input variables. The calculations used in the app utilise a unique data set comparing the efficacies of all herbicides available in New Zealand with a label claim for giant buttercup obtained from a three-year experiment on nine dairy farms in the Golden Bay district. The model used in the App is described in the peer-reviewed journal paper:

(Source: Bourdôt GW, Lamoureaux SL, Jackman S, Noble A, Chapman DF 2021. Net economic benefit of Ranunculus acris control in dairy pasture – accounting for herbicide damage to clovers and evolved resistance. New Zealand Journal of Agricultural Research