|
>
MSU Sheep Extension Program
Montana Sheep Institute
Noxious Weeds
 |
Leafy
spurge encroachment on public
land in Montana. Photo: MSU |
The Problem
= Encroachment of noxious weeds:
This problem is not just an Agricultural issue, it's
a societal issue. Non-native invasive plants are the
number one environmental threat to western wildlands.
These plants have quadrupled their range in the last
10 years. If allowed to spread at their current rate
for the next 100 years, they will be the dominant plants
on the western rangelands. It is estimated that more
than 17 million acres of public lands have serious weed
infestations and that an additional 5000 acres become
infested each day. Encroachment of non-native weeds
reduces forage availability for wildlife and livestock.
Forbs are a critical source of food supply for wildlife
species, and noxious weeds nearly eliminate the forb
component of the landscape. As a result, wildlife food
sources are significantly limited. This has an indirect
impact on wildlife-associated recreation opportunities
and expenditures in most states. This secondary impact
on the economy is unknown, but is estimated to range
between $200 to $300 million each year.
Noxious weeds gradually replace grass species until
the landscape diversity is significantly compromised.
The influence of leafy spurge, alone, drastically affects
cattle grazing utilization. When leafy spurge patches
exceed an infestation level of approximately 40% - ranchers
observe little utilization by cattle (J. Range Mange,
45:405). This results in a loss of land usage and value,
as there is minimal available cattle/wildlife grazing
and the use of chemicals to control invasive plants
exceeds the value of the land.
The Solution
= Utilization of sheep for management of noxious weeds:
 |
Sheep
from a MSI project grazing leafy spurge. Photo:
MSU |
The Montana Sheep Institute (MSI) has repeatedly demonstrated
that sheep can be used to control non-native noxious
weeds. Selective grazing of unwanted plants helps control
their growth. As their growth is limited, their roots
and strength are compromised. As a result, the lesser
grazed native plants are able to grow larger root bases
and plants and gradually re-establish themselves.
Sites involved in controlled sheep grazing demonstrate
that sheep will selectively graze leafy spurge and knapweed.
For example, in studies examining the utilization of
leafy spurge by grazing sheep, there was a 60-70% utilization
of leafy spurge and a 30-40% utilization of grass. In
similar studies looking at knapweed - there was a 50-60%
utilization of knapweed, 30-40% utilization of grass,
and 10% utilization of forbs. Over time this type of
grazing weakens the weed species and favors the re-establishment
of grass and forb species.
Most of the sites involved in the MSI program have
been depredated by weeds to a state that most traditional
weed control methods (herbicides) are economically impractical.
Therefore, utilizing sheep provides a cost effective
means of controlling weeds on these lands.
|
