Horsetail ( Equisetum arvense ) is a well-known and easily recognizable species. Until recently, it was said to be an indicator plant, characteristic of acidic and sterile soils. Today, it turns out that this is not necessarily true, and one can even hear about handsome horsetails growing on lime piles. This plant is famous for its easy adaptation to new conditions, so it is hardly surprising that it conquers such sites, especially since there is little competition from other species there.
Characteristics of horsetail
Horsetail, as its name suggests, squeaks, and one of its common names – horsetail – perfectly captures the weed’s characteristic appearance. The sound made when the stems break is caused by their high silica saturation, which we will return to when discussing methods of combating this species, as it is a difficult opponent.
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It is a perennial plant that reproduces by stolons and spores. The specific structure of horsetail is compared to an iceberg. Although the above-ground part grows to only 30 cm, the roots reach up to 2 meters into the soil, and the stolons spread at an alarming rate, being able to cover a hectare from one plant in 6 years.
For years, it was said that horsetail inhabits acidic soils. Today, it turns out that this is not necessarily true, rather people speak of unregulated water-air relations, although this is not the norm either. What is certain, however, is that this species easily adapts to new conditions, hence its expansion is only accelerating. Once found only in ruderal areas or along railway tracks, today it appears more and more often in stubble fields, as well as in plantations of plants grown in wide inter-rows.
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Combating horsetail
The harmfulness of horsetail depends on both the intensity of its occurrence and the species that infests it. In the case of mass occurrence, it is obvious that the problem is serious, but in the case of smaller occurrences, it is not necessarily so, although the threat should not be ignored. In general, cereals are largely resistant to horsetail infestation. Studies show that in the case of barley, even 50 pcs./m2 does not cause a significant decrease in yield. However, the problem occurs in the case of the aforementioned plants grown in wide inter-rows, such as corn, potatoes or sunflowers, where only 5 pcs./m2 can cause a significant decrease in yield.
When it comes to control, as with other troublesome weeds, the first thing that comes to mind is glyphosate. Theoretically, a total herbicide should be able to handle everything, but in practice it is not necessarily so rosy. Here we return to the aforementioned saturation of horsetail stems with silica, and at the same time to the small surface area of the leaves, which together result in a very limited uptake of the active substance. On the other hand, combinations of glyphosate + MCPA are considered quite effective, so in practice, due to the registration of multi-component products, it will be glyphosate + MCPA + clopyralid + fluroxypyr or glyphosate + MCPA + mecoprop + dicamba.
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Agrotechnical methods may also be a certain solution, although it should be expected that this will be work for years, with regular repetition of treatments. First of all, horsetail is sensitive to the oxide form of lime, hence it should be chosen for liming weedy sites. Another issue related to the aforementioned unregulated water-air relations will be taking care of melioration and regular deep-soiling of the field. Another solution may also be the intensification of nitrogen fertilization, which will increase the competitiveness of crops without stimulating horsetail, which is not very sensitive to the supplied nitrogen. However, it is not worth trying to plough or plate horsetail, because these treatments destroy the above-ground part, while stimulating the underground part, responsible for reproduction.
