Spectrophotometric technique for measuring herbicide deposition from wiper applicators

ABSTRACT

Weed wipers have been used to apply herbicides selectively to tall weeds in pastures for several decades, but few reliable techniques exist to quantify the relative output of wiper applicators under varying operating conditions. A new technique is described in which clopyralid is applied by wiper applicators to plastic sleeves on uniform, upright, flexible posts with herbicide deposition quantified using a spectrophotometer. The technique was used to compare the relative output of three commercially available wipers: the Rotowiper, Eliminator and Weedswiper. At a constant speed of 5 km/h, large variability was found in the quantities of herbicide deposited by the three wiper applicators. When applied at a range of speeds, there was a small negative correlation for herbicide output as speed increased, although variability in output resulted in this trend being significant for the Weedswiper, but not for the other wiper applicators. The Weedswiper applied less herbicide than the other two wipers, although the relative output from the Eliminator compared with the Rotowiper differed between the two experiments.

KEYWORDS:

• Application
• clopyralid
• Eliminator
• Rotowiper
• spectrophotometer
• weed wipers
• Weedswiper