Equisetum: From the Ditch to the Field

May 20, 2022
ICM News

Scouringrush (Equisetum arvense) and field horsetail (Equisetum hymale) are two species of the Equisetum genus found in Iowa. There are 15 Equisetum species worldwide. They are primitive perennials that produce spores rather than seeds and spread primarily by rhizomes (underground stems). These two weeds are commonly found in roadside ditches, preferring poorly drained soils. More information about scouringrush, its lifecycle and its history can be found here.

Field horestail in corn field.
Figure 1. Field horestail in corn field.


Scouringrush invading no-till soybean field.
Figure 2. Scouringrush invading no-till soybean field.

While individual shoots of scouringrush and field horsetail are not highly competitive, dense colonies can interfere with crop production. Tillage can suppress the weeds, but it probably would take several years of intensive tillage to eradicate them from fields. Unfortunately, tillage can break rhizomes of both species into small pieces and spread them throughout the field.

The architecture of the equisetum’s canopies reduces the area for herbicide absorption, making them particularly difficult to manage with herbicides. Herbicides used in crop production do not provide significant control/suppression of equisetums.

Most infestations of these weeds are due to a source population in adjacent non-crop areas. Controlling the equisetum in these areas probably is the most efficient method of removing them from crop fields, but unfortunately this is not an easy task, either. Repeated mowing or tillage is one option, but again it will take several years of disturbance to control/eradicate the weed.

Chlorsuluron (Telar) is one herbicide that has good activity on equisetums, but is only registered for use in non-crop sites such as roadsides. Chlorsulfuron is a sulfonylurea herbicide (Group 2), related to products such as Accent and Classic. Multiple applications would be needed for complete control. UNL researchers conducted a study near Murdock, Nebraska with several herbicides and reported chlorsulfuron provided the most effective control of scouringrush. However, chlorsulfuron is a persistent compound that is toxic to both corn and soybeans, so caution must be taken to prevent overspray into production fields.

Chlorsulfuron is recommended at 1.0 to 2.6 oz/A (75% dry formulation) for controlling equisetums. Spot applications at higher rates are allowed in certain locations according to the product label. An 8 oz. container is the smallest quantity that could be found on the internet. This container would provide sufficient herbicide to treat approximately a mile of a 20 ft. roadside twice at the intermediate rate.

Purdue University researchers evaluated the efficacy of spring or fall applications of several other herbicides on mowed and unmowed scouringrush. When mowing, it was necessary to allow some regrowth of new plant stems prior to herbicide application, to produce desirable control with herbicides. Unmowed scouringrush did not produce acceptable results.

Researchers reported that mowed scouringrush treated in the fall with aminopyralid (Milestone) and imazapyr (Habitat) may provide additional effective options in non-crop areas for controlling scouringrush populations. In unmowed populations, biomass of scouringrush was not reduced at 42 days after application. Aminopyralid and imazapyr are not labeled for row crops and have a lengthy rotation restriction.

Regardless of the management tactic chosen, persistent effort is important to eliminate equisetum populations. Focusing efforts outside of crop fields on the adjacent source area in addition to suppression in the crop field is likely to yield the best results.


Bernards, Mark, et al. “UNL CropWatch June 16, 2010: Controlling Scouringrush.” CropWatch, University of Nebraska - Lincoln, 16 June 2010, https://cropwatch.unl.edu/unl-cropwatch-june-16-2010-controlling-scourin....

Zimmer, Marcelo, and Bill Johnson. “Scouringrush Control near Drainage Ditches in Corn and Soybean Fields.” Pest&Crop Newsletter, Purdue University, 17 Apr. 2020, https://extension.entm.purdue.edu/newsletters/pestandcrop/article/scouringrush-control-near-drainage-ditches-in-corn-and-soybean-fields/.


Links to this article are strongly encouraged, and this article may be republished without further permission if published as written and if credit is given to the author, Integrated Crop Management News, and Iowa State University Extension and Outreach. If this article is to be used in any other manner, permission from the author is required. This article was originally published on May 20, 2022. The information contained within may not be the most current and accurate depending on when it is accessed.


Gentry Sorenson Field Agronomist in NW Iowa

Gentry Sorenson is a field agronomist in Northwest Iowa for Iowa State University Extension and Outreach. He works closely with farmers to offer educational programming in crop management issues.  He also works with agribusinesses, pesticide applicators, certified crop advisors, and other in...

Meaghan Anderson Field Agronomist in Central Iowa

Meaghan Anderson is a field agronomist in central Iowa and an extension field specialist at Iowa State University Extension and Outreach. Educational programming is available for farmers, agribusinesses, pesticide applicators, certified crop advisors, and other individuals interested in...