The main problem with common names is that some plants may be described by 10 or more names. Field horsetail (Equisetum arense) is one of those species--while the species is easily distinguished from any other plant due to its unique growth habit, the myriad of names used to describe the plant leads to confusion in its identification.
Horsetail has become more prevalent in Iowa roadsides as maintenance programs for these areas have been reduced. While the plant can reproduce by spores, the primary means of spread is an extensive rhizome system that may reach depths of 4 to 5 feet. An increasing problem is the expansion of patches originating in non-crop areas into crop fields. Although horsetail does not appear to be highly competitive, it can reach densities where it interferes with corn or soybean yields.
The best approach to managing horsetail is to attack the source of infestation, typically a non-crop area adjacent to the cropland. Unfortunately, the plant is difficult to control regardless of where it is found. Repeated tillage or mowing should eventually exhaust the underground energy reserves, but it probably will take at least two years of repeated disturbance to bring the plant under control. In crop land, tillage should reduce the competitiveness of horsetail with crops, but it is unlikely to eliminate the plant once it has become established. Tillage may actually enhance the spread of the plant within the field by dragging rhizome pieces throughout the field. While horsetail is not listed on the label, products containing flumetsulam (Python®, Hornet®) are reported to have activity on this weed. Horsetail is listed on the Permit® label.
A bulletin providing more information on the biology and management of horsetail is available on the Iowa State University Weed Science Web page.
Horsetail invading a soybean field from an adjacent non-crop area. (Bob Hartzler)
This article originally appeared on pages 143-144 of the IC-496(13) -- May 30, 2006 issue.