Horsetail

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Control of Horsetail (Equisetum species) with Roundup Pro Biactive

Horsetails are a family of weeds not to be confused with Mare’s tail, (Hippurus vulgaris), which is an aquatic plant of an entirely different species. E.Arvense, (Common Horsetail or Field Horsetail) is the most widely seen but there is also Marsh Horsetail, (E. palustre) and Wood Horsetail, (E. sylvaticum). The Horsetail family consists of a single genus of a lower order of plants which has survived since the Carboniferous age when the coal measures were laid down and can be seen fossilised in ancient rocks.

Growth Habit

It is a perennial with creeping, rhizomatous stems, which can penetrate 2 metres into the soil. Much of the spread of the plant is vegetative by these rhizomes, but a sexual fruiting stem carrying a sporulating fruiting body emerges in the spring to about 25cm in height. It is brownish white and hollow terminating in a cone-like structure bearing sporangia on their scales. The spores are ripe in April when the sporangia burst, liberating their spores before dying down. Barren, pale green, jointed stems then emerge to 30 - 60cm in height and bare slender, simple branches in place of leaves in whorls of up to 12. It is these stems which are increasingly seen as a problem in waste ground, non-cropped areas, gardens and fallow land.

The stems contain large amounts of silica, it has also been called Scouring rush and was said to be used by milkmaids to clean milk pales.  Most species of Equisetum are poisonous to livestock by virtue of alkaloids and the enzyme Thiaminase, which destroys Vitamin B1 and causes animals to suffer from Vitamin B1 deficiency. Horsetails are usually avoided by grazing livestock, but should never be fed to livestock in hay or silage.

Control Methods

Drainage in wet areas, liming where necessary and repeated cutting of the vegetative shoots can all contribute to controlling the weed. In practice frequent cutting would take years to exhaust the rhizomes. Cutting of the spore-bearing shoots before sporulation also helps minimise new plants.

MCPA and 2,4-D give control of aerial shoots but re-growth from rhizomes occurs the following year. Asulam also gives some control. Sowing intervals need to be carefully observed with these herbicides.

Some residual herbicides like sodium chlorate and dichlobenil give control of Equisetum but cropping is restricted or excluded after their use. Their application can be useful in areas of ingression to create a sterile barrier between adjacent contaminated ground and pastures.

Control with Roundup Pro Biactive

Thick layers of silica and wax make the cuticle very difficult to penetrate with herbicides and the needle-like ‘leaves’ present a very small area for interception of spray. This physical barrier, combined with a large area of underground storage organs, mean this weed is usually classed as resistant or only moderately susceptible to glyphosate.

To maximise control in areas where an alternative residual weed control is not possible or where re-cropping of the area is planned it may be necessary to use a non-residual, environmentally acceptable herbicide and the following will optimise control with Roundup Pro Biactive:

Foliar Spray

  • Use a Biactive formulation of Roundup with its superior wetters and consider adding up to 2% Mixture B NF or Ethoxylated Tallow Amine wetter.
  • Wait until the vegetative shoots have reached maximum height (60cm), usually July.
  • Bruise the stems lightly immediately before treatment. This will break the waxy layer and allow much better penetration of the glyphosate. To achieve this small areas can be brushed with a stiff broom, field areas are best with a Cambridge roller. The bruising must not be severe enough to break off the stems.
  • Apply the highest rate of Roundup Pro Biactive recommended.

Weedwiper

  • A weedwiper could also be used and the effect of wiping itself can help in the bruising process.
  • On small areas or where the weed is encroaching amongst other desirable plants the use of a weed wiping glove, (like the Croptex™ Glove), can also prove a very successful method of bruising and application at the same time.

Stem Injection

  • Where the infestation is in a position where spraying is not practical or to eliminate the last few stems after previous spray treatments a stem injection method can be adopted. Although it is labour intensive there may be situations where it is justified.
  • It is legal under the general chemical thinning recommendation on the forestry approval to inject Roundup Pro Biactive into each hollow stem using an injection tool, or alternatively the stem could be cut at the first segment above the crown and the herbicide introduced using a spot gun or a medical syringe with no needle.
  • Cut stems should be removed from grazing areas before stock are returned.

All Methods

Monitor and re-treat sites as necessary over a period of 3 years.

Dose Rates, Timings and Water Volumes

MethodDose Rate of Roundup Pro BiactiveDose Rate of Roundup ProBiactive450Application Advice
Foliar Spray 10l/ha in 100-200l water, in a knapsack 50ml per litre water 8l/ha in 100-200l water, in a knapsack 40ml per litre water Add 2% Mixture B NF or ETA Wetter, use droplets on the finer side of medium, spray to just before run-off
Weed wiper1 part Roundup Pro Biactive in 2 parts water1 part Roundup ProBiactive450 in 3 parts waterThe effect of weed wiping can help the bruising process
Stem Injection Inject 10ml per stem of a 20% solution of Roundup Pro Biactive and water Inject 8ml per stem of a 20% solution of Roundup ProBiactive450 and water Inject into each hollow stem