Habitat and Biology
Field horsetail thrives in many
habitats and is just at home in wet, poorly drained areas of
fields and grasslands; wet meadows; streams and other sites with
high water tables as in well drained sites in farm fields,
orchards and nursery crops, and in sites with sandy or gravelly
soil such as along roadsides, railroad tracks and beaches. In
general, horsetail appears most commonly in acidic and wet soil
conditions.
Buds and tubers on the rhizomes
are capable of reaching the surface from great depths. Single
rhizome segments 0.5 inch long planted 6 inches deep easily
produced new plants (Cloutier and Watson, 1985). Plants can only
tolerate shade for short periods unless they have sizable
quantities of carbohydrates stored in the established rhizomes.
Tuber production drops rapidly as shade levels increase;
conversely tuber production is optimized when plants grow in
full sunlight. Horsetail responds to potassium and its growth is
optimal in soils with high available K levels (Andersson and
Ludegardh, 1999b).
Field horsetail never produces
flowers or seeds; rather, it reproduces by spores, horizontal
rhizomes and tubers. Little information on the frequency or
conditions required for establishment via spores was found in
the literature. We do know that fertile stems are seldom
observed in cropped land. Fertile stems develop early in the
spring and a single spore cone can release millions of minute
spores (0.1 mm across). These are viable for about 48 hr after
being released and germinate only in damp soil (Royer and
Dickinson, 1999). "Sporelings" are very small and any
soil tillage or herbicide application at this stage should
destroy most if not all potential horsetail plants. Thus, spores
are unlikely to be an important means of horsetail propagation,
particularly in cropped land.
Horsetail rhizomes extend for long
distances and are often 3 feet or more below the ground surface.
Mitch (1992) says it well: "Horsetail’s upper growths are
like surfaced periscopes, giving no indication of the
industrious bulk of underground parts." Rhizomes send up
numerous aboveground shoots of two different types at various
times of the year. Tubers are primarily food storage organs but
develop into new plants if removed from the rhizome.
Sterile shoots of horsetail (those
that look like small pine trees) appear in early May and reach a
maximum growth rate in July, maximum shoot height in August, and
maximum shoot number in September (Marshall, 1985). Rhizome
growth accelerates rapidly between June and July and peaks in
October. Tubers appear in July and increase in weight until a
killing frost occurs.
Horsetail Importance and
Management in
Agricultural Settings
Field and Vegetable Crops Prevention
is always preferable to control. Movement of rhizomes or tubers
on tillage implements is a common means of starting new
populations. Simulations done to predict the rate of spread
estimate that six years after introducing horse-tail into an
agricultural field, the weed will infest 2.5 acres (Cloutier and
Watson, 1985)! Check field edges and low areas of fields
periodically for possible horsetail infestations. The best means
of controlling this weed is through quarantine and mechanical
and cultural methods while it infests only small areas. Cultural
practices such as improved drainage and adequate lime and
fertilization programs will help suppress horsetail infestations
in any habitat. Applying nitrogen fertilizer to grass crops is
helpful because horsetail responds minimally to nitrogen while
grass crops respond quickly and significantly. This gives the
crop a highly competitive advantage over horsetail because this
weed is shade sensitive (Andersson and Ludegardh, 1999a).
The impact of field horsetail on
crops is highly correlated to the competitive ability of the
crop. This weed seldom has economic impacts in vigorous,
well-managed corn, soybeans or small grains. However, it
competes vigorously with slow growing and short statured
vegetable crops and can become a dominant monoculture in
landscape plantings. Most producers succeed in harvest-ing
productive crops by incorporating tillage, competitive crops
and, in the case of vegetable, mulches into their management
system.
In Finland, horsetail populations
decreased noticeably between the 1960s and 1990s due to improved
small grain cultivation techniques and more competitive
varieties (Ervio and Salonen, 1987). Horseweed’s extensive and
deep rhizome system means that tillage and cultivation alone
only destroy the top growth and delay reestablishment. Field
crop producers who practice a reasonable annual tillage program
and maintain a competitive crop in an infested field for several
years might eradicate horsetail.
There are few herbicides that
affect field horsetail in field crops. Primisulfuron (Beacon)
can give reasonable burning action on horsetail in corn but
preplant tillage followed by in-row cultivation is often as
effective. Repeated applications of MCPA reportedly reduce
horsetail infestations and would be safe to perennial grasses
such as bluegrass and pasture grasses. Thorough preplant tillage
and narrow row soybeans probably offer the best horsetail
suppression in this crop.
Livestock Poisoning. While
medicinal uses of field horsetail are reported, plants can be
poisonous to animals and cause a disease known as "equisetosis."
Many substances (including aconitic acid, equistitie, nicotine,
palmitic acid and silica) have been associated with animal
poisoning, but the causal agent is believed to be thiaminase,
either alone or in conjunction with one or more additional toxin
(Hill and Foland, 1986).
Horses are particularly sensitive
and can be killed if large amounts of horsetail are consumed.
Hay containing 20% or more horsetail produces symptoms in horses
in two to five weeks. Symptoms include unthriftiness followed by
weakness, "staggers," nervousness, faulty vision, and
difficulty in turning. In advanced stages, horses may "go
down" and not be able to rise. Such animals are nervous and
make frantic efforts to stand (Hill and Foland, 1986). The
appetite remains normal until death. In late stages, muscular
rigidity and constipation may be observed. In fatal cases, death
is preceded by quiescence and coma. The immediate removal of
contaminated forage brings about rapid recovery. Keep poisoned
animals out of rain and adverse weather. Cattle, sheep, and
goats are rarely poisoned. Always consult a veterinarian if
poisoning is suspected.
Presence and Control in
Non-cropland Horsetail
is becoming more common in non-cultivated sites such as
roadsides, flower beds, lawns, ornamental plantings and sandy
beaches. Even if repeated tillage could be done, it may not be
successful. Horseweed’s extensive and deep rhizome system
means that tillage and cultivation only destroy the top growth
and delay reestablishment. The density of many perennial weeds
can be greatly reduced with a season of repeated tillage.
However, weed scientists in Canada hand-weeded an area with
horsetail 16 times during one summer. The following year these
plots looked identical to the check plot (Cloutier and Watson,
1985)! Even glyphosate fails to control horsetail. A home owner
reported using glyphosate three times in one season to kill
horsetail: the next year the site sported a dense monoculture of
horsetail.
The Weed Control Manual 2000
(Curran, et al., 2000) lists only two herbicides for field
horsetail control in non-cropland, ornamentals/woody plantings,
small fruits and deciduous tree fruits: diclobenil (Casoron) for
all of the above sites/crops; and clorsulfuron (Telar) or
sulfometuron (Oust) for non-crop areas. No references on the
long term effects of these herbicides on horsetail were found.
Follow label guidelines carefully if either of these herbicides
is used.
Summary
It is easy to recognize this
perennial weed because in the vegetative phase field horsetail
looks like a small pine tree. The reproductive phase is also
very distinctive with the hollow stems that pull apart like
stove pipe with a spore head on the top. Field horsetail
suppression (and possibly eradication) will only result if the
appropriate mix of practices is done as a sustained effort for
several seasons.
References
Andersson, T.N. and B. Ludegardh
1999a. Growth of field horsetail (Equisetum arvense)
under low light and low nitrogen conditions. Weed Sci. 47:
41-46.
Andersson, T.N. and B. Ludegardh
1999b. Field horsetail (Equisetum arvense) - effects of
potassium under different light and nitrogen conditions. Weed
Sci. 47: 47-54.
Cloutier, D. and A. Watson. 1985.
Growth and regeneration of field horsetail (Equisetum arvense).
Weed Sci. 33: 358-365.
Curran, W. et al. 2000. Editors.
Weed Control Manual 2000. Meister Pub. Co. Willoughby, OH. 562p.
Ervio, L-R. and J. Salonen. 1987.
Changes in the weed population of spring cereals in Finland.
Ann. Agric. Fenn. 26: 201-206.
Hill, R.J. and D. Foland 1986.
Equisetum. In: Poisonous Plants of Pennsylvania. Dept. of
Agric., Bureau of Plant Industry. Harrisburg, PA. Pages 67-68.
Marshall, G. 1985. Studies on the
growth and development of field horsetail (Equisetum arvense).
Weed Sci. Soc. Amer. Annual Meeting. Abstract no. 179.
Mitich, L. 1992. Intriguing World
of Weeds: Horsetail. Weed Technol. 6: 779-781.
Royer, F. and R. Dickinson. 1999.
Common horsetail. In: Weeds of the Northern U.S. and
Canada. Univ. of Alberta Press. Edmonton, Canada. Pages 216-217.
May, 2001
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