Volume 1 Issue
7
July 2, 2004
Managing Field Horsetail
Common or “field horsetail” is in the same family
of plants as Scouring-Rush (Equisetaceae) and reproduces by emitting
spores from its cone-like structures. One concern with this plant is
its toxicity (thiaminase) to grazing animals. Horses are the species
most affected, however, cattle and sheep may be affected, but this
occurs rarely as they tend to avoid the plant. Thiaminase causes
deficiency of thiamine is animals and a veterinarian should be
consulted to assist in the treatment of this deficiency. Consumption
of horsetail in feeds is the most likely route of poisoning, but
fresh plants are also toxic although considered unpalatable in most
animals.
  Horsetail
is fairly easy to recognize: Two types of shoots 1 to 3 feet tall
merge from horsetail’s underground rootstock (Fig 1). Both types are
round, hollow, stiff, and jointed. The stem sections easily pull
apart. The first type of shoot (Fig. 2) although not commonly seen
in cropped fields, appears earlier in spring, and ends in a
terminal, cone-like spore producing structure.
  The later appearing
sterile shoot (Fig. 3) bears whorls
of pine-needle-like branches and looks like a horse’s tail. Figure 4
shows the current growth stage of the sterile structure as it
appears in fields today.
Horsetail commonly grows on shaded, moist soil in meadows, along
roadsides, in ditches and thickets, along stream banks, at the
borders of swamps, and on railroad embankments. Wet weather favors
the establishment of this plant into
new areas such as field edges particularly where the water table is
close to the soil surface. Thereafter, tillage can move horsetail
rhizomes into other areas of the field. Once horsetail is
established on a field it is difficult to eradicate.
 Research
conducted by P. Sikkema at the University of Guelph shows that
in-season control of horsetail is possible with several herbicides
(Table 1).
 Several crop producers with horsetail problems
in
soybeans have indicated that glyphosate applied at rates up to 1
qt/a did not have any visible effect on the plant this spring.
Sikkima reports that horsetail will respond to glyphosate if the
rate is high enough (Fig 5). Horsetail is moderately
tolerant of glyphosate and patches should be sprayed with at least 2
qts/acre for in-season suppression.
Carlyle Holen—Extension IPM
Specialist—NW Minnesota
Bobby Holder—UMC Soil Scientist
|
