Herbicide deposition on weeds from weed wipers

Abstract

Weed wipers available in New Zealand vary in their mechanisms for delivering herbicide The objective of this experiment was to measure clopyralid output from three weed wipers using a standardised methodology The herbicide output for the Eliminator Rotowiper and Weedswiper was investigated at different speeds of application The herbicide was applied to artificial weeds covered in plastic sleeves folded at the base to collect drips while the three wipers were driven over the artificial weeds The sleeves were then removed and washed with water The resultant solution was then analysed for clopyralid using a spectrophotometer and a predetermined calibration equation The experiment showed there was no relationship between the speed at which wipers were pulled and their herbicide output The Eliminator and Rotowiper had on average twice the output of the Weedswiper although their output was more variable than that of the Weedswiper Because of the variability in output in some wipers the concentration rates to be used in each wiper need to be high enough to compensate for occasional low quantities being wiped on weeds