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Massasauga rattlesnake | The wild thing for the week of 8/18/08
Figure 1
The reproductive stems of field horsetail. Notice cones
on top and leafless stalks.
Field horsetail, Equisetum arvense, is a perennial with a spreading rhizome system from which new plants arise. Field horsetail is known by a variety of different common names, usually dependent on where you are in the state. Some call it scouring rush, some call it ribbon grass, and it is even called "poor-man's-tinker toys" in some areas. As with johnsongrass or any other perennial plant that has rhizomes, the underground root structures are what make these plants difficult to control.
Field horsetail is also unique in that two types of stems, and two different types of growth habits, occur within the same plant. The first type of stems to appear in the early spring are the unbranched, reproductive stems (Figure 1). These stems have cones at their ends, are often whitish to pink in color, round in cross-section, without leaves, and often grow to one or two feet in height. The second type of stems or growth habit that appears later in the season are the vegetative stems. These are highly branched and resemble a horse's tail, thus the name (Figure 2).
In Missouri, field horsetail is probably most common in wet areas such as ditchbanks around corn and soybean fields. It has a tendency to encroach into the low-lying or wet areas of these fields from the ditchbanks and it will thrive in these areas once it is established. Since it has rhizomes, any kind of shallow tillage such as chisel plowing or disking only serves to spread the rhizomes and magnify the problem.
Few herbicides provide effective control of field horsetail in either corn or soybean. Many studies have shown that standard and even high application rates of glyphosate are virtually ineffective on this species. Some research conducted by weed scientists in Canada has shown that in corn, sulfonylurea herbicides like Beacon and Permit in combination with dicamba (Banvel, Clarity, Distinct) should provide about 80 percent field horsetail control during the season of treatment as long as the applications are made to the vegetative stems. Given the nature of its extensive root system, it is not certain how much long-term field horsetail control is actually provided by these treatments, but at least the competitive effects of this weed are being reduced during the season of treatment. This research has also revealed that Python and Hornet are some of the only preemergence herbicides that will provide some degree of residual control of field horsetail, so inclusion of this product in with a burndown herbicide is another option to consider.
In soybeans, glyphosate in combination with Python as a preemergence burndown treatment is one of the only options available for field horsetail. As mentioned previously, Python is one of the only products that offers any residual activity of field horsetail. And, unfortunately, no effective postemergence treatments have been identified in soybean. Follow-up applications of glyphosate will only provide minor suppression at best.
In noncrop areas (which on some labels includes non-irrigation ditchbanks), Telar, Oust, and Surmount are a few of the herbicides that are labeled for application on field horsetail. Each of these herbicides is very persistent and can cause severe injury to crops so extreme care should be taken when applying these herbicides near or in areas that will be planted to corn and soybean.
Figure 2
The vegetative stems of field horsetail. Notice high degree of branching and similarity to a horse's tail.