While it may have a benign sounding name, horsetail itself is anything but. Knowing that this weed has survived on Earth for more than 300 million years and is called a living fossil tells you almost everything you need to know about the challenges of controlling it – it’s nearly impossible.
Still, there are chinks in horsetail’s armour where herbicides can slow it down long enough for your crop to get ahead. In Enlist E3™ soybeans, a program approach to horsetail involves pre- and post-emergence applications of Enlist™ herbicides that target the weed’s reproductive stages and top growth.
The problem: Field horsetail is a flowerless, seedless, highly competitive perennial weed that grows well across a wide range of conditions, although it does not survive in well-shaded areas.
Horsetail’s “roots” are tuber-bearing rhizomes that spread horizontally underground, and they can also go quite deep – anecdotal evidence has found horsetail rhizomes as far as six metres down in the soil. The tubers reside in the deeper parts of the root structure and stay dormant as long as the rhizomes they’re attached to are alive. If those rhizomes are separated from the main network (through cultivation, for example) or die, the tubers “wake up” and start generating new plant stems.
Horsetail is dimorphic – meaning it has two different physical forms depending on the time of year. In early spring, vertical shoots emerge as a single stem tipped with long, cone-shaped, spore-producing heads. When these die back, the familiar hollow-stemmed plants with leaf-like foliage take over.
Controlling horsetail with the Enlist weed control system: Effective horsetail management is focused on controlling top growth, particularly the spore-bearing shoots that appear in spring. Attempts to eliminate below ground rhizomes and tubers only serve to encourage new growth and spread.
Because horsetail is such a strong survivor, growers need to take a multi-year, multi-pronged approach to get it under control. This includes repeated use of cultural methods, such as mowing and shading, as well as herbicide use. The thinking is that repeated removal of top growth year after year slowly drains the plant of underground reserves and reduces the rhizome biomass enough that it eventually dies. It’s a commitment, to be sure – horsetail does not die out easily or quickly.
On the plus side, field horsetail is extremely sensitive to 2,4-D, making the Enlist weed control system, which includes two 2,4-D-based herbicide options, a powerful tool for those growing Enlist E3 soybeans. These varieties are tolerant of glyphosate, glufosinate and 2,4-D and can be safely sprayed with:
Both herbicides come with Colex-D™ technology for near-zero volatility and low drift so it stays where it’s sprayed.
The program approach to control horsetail: This is a two-pass system for Enlist E3 soybeans that targets horsetail shoots in early spring, as well as the green top growth that appears once those shoots die back.
Key takeaways: The key thing to remember about field horsetail is that it is a tenacious survivor and getting it under control takes time and patience. A two-pass herbicide program targets both shoots and green top growth is a good strategy to both reduce weed competition and to chip away at the rhizome biomass underground.
While effective herbicide options for horsetail are limited, the Enlist program approach allows farmers to apply 2,4-D – a herbicide this weed is extremely sensitive to – twice in a season so that the yield potential of your soybean crop is protected.