Is it possible to control field horsetail?
The quick answer is NO. Sorry. There is no silver bullet. Unlike other weed problems where we have solutions, field horsetail is a plant where there is no easy answer. That's probably the reason why field horsetail has been around since the Carboniferous age more than 300 million years ago. It is part of the ancient genus Equisetum, a prehistoric survivor and one of the toughest weeds to manage.
What is field horsetail?
Field horsetail is a perennial that grows from a tuber-bearing rhizome. This root system comprises actively growing rhizomes that can penetrate to greater than 1 m in depth, from which green fern-like fronds grow each year (looks like a small pine tree). Attached to the deeper rhizomes are small tubers which remain dormant while the rhizome stays alive. When the rhizome dies or becomes detached due to cultivation or other means, the tubers initiate growth to produce new plants.
Controlling field horsetail
It is best to get field horsetail under control before you plant. Several herbicides provide some level of top growth control ONLY because it is difficult to get the active ingredient to depths deep enough to control the rhizomes and tubers. Few herbicides are registered and their use is dependent on the situation in which horsetail grows.
Herbicides registered for field horsetail top growth control
Note: there are also several Group 2 herbicides, including halosulfuron that list suppression of field horsetail. Tank mixes with MCPA are recommended, if MCPA is registered on the specified crop.
The most effective strategies are based on many years of repetitive attacks on the above ground plant in an attempt to deplete the reserves to the point that the plant dies. Repetitive attacks should include herbicides, shading, mowing and hand weeding. But, as noted earlier, killing the plant will release the tubers to grow and start the cycle again.
My best advice is to remove new stands of field horsetail immediately before they spread. Established stands will take a lot of persistence to manage. Cultivation should be kept to a minimum because in most cases it will spread the rhizomes and tubers around the field allowing plants to regenerate in new parts of the field or in new fields if you forget to clean your equipment between fields. Black plastic sheeting has been found to kill or suppress rhizomes in the upper layers of the soil, however; emerging stems can penetrate some woven polypropylene mulches.
I guess we shouldn't expect an easy way to manage a weed that has survived 300 million years!
Figure 1. Field horsetail rhizomes.
Figure 2. Field horsetail in strawberries.
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