Chemical control of field horsetail (Equisetum arvense)

Field horsetail is a perennial, rhizomatous weed with summer-growing fern-like foliage and sporelating stems. It likes moist, free-draining sandy soils and gravel riverbeds and flood plains. Glasshouse experiments on 10-month old potted field horsetail plants showed excellent efficacy of imazapyr, amitrole, metsulfuron, picloram and combinations of picloram with metsulfuron or triclopyr, all at highest recommended rates. However, in the field trial, single applications of these herbicides did not provide effective long-term control with significant regrowth 2 months after treatment. This suggests that most of the herbicide treatments did not damage the extensive root system sufficiently to stop considerable regrowth, with herbicides such as triclopyr+picloram, glyphosate and metsulfuron failing to give adequate control of this weed in the field. Further applications of amitrole or triclopyr+metsulfuron 2 months after the initial treatment gave better results but also killed all other vegetation.