As agricultural producers continue to monitor their growing crops, agronomists from the Iowa State University Extension and Outreach are providing information on two species of Equisetum found in Iowa: scouring rush and field horsetail. While there are 15 known species of Equisetum known worldwide, these are the two that are commonly found across the state, usually in poorly drained soil.
The weeds are primitive perennials that produce spores rather than seeds. They typically spread via rhizomes, which are underground stems. The individual shoots of scouring rush and field horsetail are not competitive, but together, they can impact crop production. Although tillage can help suppress the weeds, it can also backfire by breaking the rhizomes and spreading them throughout the field.
Controlling equisetum can be difficult for agricultural producers as well. Although repeated mowing and tillage can help, the impact may not be seen for several years. One option farmers can try is chlorsulfuron, an herbicide that can potentially control the weed after several applications. Chlorsuluron is recommended at a 75% dry formulation, and spot applications at higher rates may be permitted in certain locations, depending on the details of the product label.
Agricultural producers can mow the scouring rush in the fall and treat it with aminopyralid and imazapyr in non-crop areas. However, it’s important to note that they are not labeled for row crops and have extended rotation restrictions.
In general, the agronomists claim that persistent effort is essential to eliminating equisetum populations. It’s best to focus on the areas outside of crop fields, in addition to suppression in the crop fields themselves, for the best results.