Wiper Application of Herbicides to Cirsium arvense

Abstract

Wiper applicators allow herbicides to be selectively delivered to upright target weeds, thereby avoiding application to nearby lower-growing desirable pasture plants. In this research, we investigated the efficacy of wiper application of four herbicides, clopyralid, metsulfuron, glyphosate and a triclopyr/picloram mixture, to control Cirsium arvense (L.) Scop., a troublesome weed of pastures in New Zealand. The results showed that wiper application of herbicides was a useful technique for controlling C. arvense. In one trial when plants were treated at the post-flowering stage, stem density reductions in the following season of 93%, 90% and 82% were achieved following a double pass with a rotary weed wiper containing glyphosate, clopyralid and metsulfuron, respectively. A double pass gave better control of dense infestations of C. arvense than a single pass for glyphosate and triclopyr/picloram, but not for clopyralid and metsulfuron. Despite wiper applicators usually being selective, some damage to pastures was recorded, very likely due to rain falling soon after wiper application. Overall, the results of this study revealed that wiper application can be used to selectively control C. arvense when the plants are treated at the post-flowering stage, though only if plants are actively growing. In addition, among the herbicides tested, glyphosate appears to be the best choice when using weed wipers to manage C. arvense, as this herbicide caused the least damage to pasture plants if washed off afterwards by rain.