What is a weed?
Any plant that occurs
where we don't want
it to occur.
What is a noxious weed?
Any plant that causes significant economic
and/or environmental
damage. A weed is a pest! "Noxious
weeds are non-native plants that have been introduced accidentally or
as ornarnentals in peoples' gardens. Some are poisonous to humans and
livestock and most grow rapidly and are extremely difficult to control.
They can reduce crop yields, displace desirable plant species, destroy
beneficial native habitat, damage recreational opportunities, clog
waterways, and diminish land values." (1)
Why should we care about weeds?
When they invade an area, many aspects of the
environment are
affected. These included:
1. Decreasing grazing for livestock and wildlife.
2. Decreased diversity therefore, decreased stability of the ecosystem.
3. Increased soil erosion.
4. Decreased water quality and fish habitat.
5. Decreased amount of food we can produce through ranching and
farming.
6. Decreased tourism.
7. Weeds kill the good plants.
Do weeds hurt farmers and ranchers?
Montana farmers and ranchers spend $ 100
million a year just to
control weeds. This money could be spent in other areas of the economy.
Yes, they can kill farmers plants and crops. They can kill ranchers
livestock.
Do weeds hurt our economy?
Studies show that knapweed alone costs
Montana's $42 million in
lost tourism every year. This $42 million in list dollars would support
500 well paying jobs in Montana.
Why are many weeds hard to kill?
1. They produce many seeds and thus spread rapidly.
2. They have deep roots thus they are hard to kill.
3. They are not palatable to livestock and wildlife therefore, these
grazers eat the other desirable plants first, leaving the weeds to
flourish.
4. They are invader species. They are adapted to rapidly colonize
disturbed areas.
5. They have allelopathy- they give off chemicals that inhibit the
growth of other plants.
6. They have waxy leaves so herbicides do not stick to the plant and
cannot kill it.
How do we control these unnatural, unwanted foreign invaders?
No one way completely works so our best strategy is
a mixed bag of
methods. This is called: Integrated Pest Management (IPM)
The methods:
1. Prevention- Keeping weeds out in the first place.
2. Chemical- Using chemicals such as herbicides that kill or retard the
growth of weeds.
3. Biological Control- Using beneficial creatures such as insects or
fungi that damage the weeds. (use of insects, domestic animals,
pathogens etc.) (2)
4. Mechanical- Tilling (plowing) or hand pulling the weeds.
5. Controlled Burning- Safely burning the weeds.
6. Grazing- Using grazing animals such as sheep or goats that will eat
the weed.
7. Revegetation- Revegetation a disturbed site to block or choke out
the
weed.
8. Physical (hand pulling, cutting, mowing, digging, disking, plowing,
burning. etc.) (2)
9. Cultural (development of weed prevention programs, weed free forage,
weed free gravel, vehicle washing, etc.). (2)
"Often, you may obtain best results by using several of these control
methods together. For example, burn and re-seed in the first year, spot
treat remaining plants with herbicides in the second year, change to
fall grazing and restrict vehicle use in the area. You may obtain
advice
on control methods, as well as specific, local concerns from local land
managers, extensions specialists, and weed control specialists.
After performing weed control, you may find it necessary to
perform site restoration." (2)
Have noxious weeds been spreading over the past 100 years?
Yes. They have been spreading at an alarming rate.
For example, spotted
knapweed arrived on the west coast in 1893 on the San Juan Islands in
Washington. By 1920, this weed has established over 24 countries in
three northwestern states, with several large infestations near
Missoula, MT. Now, spotted knapweed is established in the western
United States and has invaded all counties and about 5 million acres in
Montana alone.
Can noxious weeds cause the loss of wildlife habitat?
Yes. Dense infestations of noxious weeds
reduce wildlife forage,
alter thermal and escape cover, change water flow and availability to
wildlife, and may reduce territorial space necessary for wildlife
survival. Areas dominated by leafy spurge receive less use by deer (3
times less use) and bison (4 times less use) compared with similar
infested areas. Elk use increased about 4 times after controlling the
dense spotted knapweed infestation on study sites.
Can noxious weeds displace threatened and endangered species of
plants and animals?
Yes. Rare, threatened, and endangered
species, such as bulrush,
dwarf spikerush, bog turtle, Sacramento thistle, sapphire rockcress,
and Colorado butterfly are being displaced by noxious weeds.
Can noxious weeds alter the functioning of Riparian (wet land)
areas?
Yes. This weed lowers water tables and, in
some areas, has
eliminated surface water and native vegetation needed by
wildlife. The noxious weed (tree) saltcedar is drying up ponds
and small streams in some areas.
Can noxious weeds reduce forage production for livestock and crop
production?
Yes. Leafy spurge and spotted knapweed can
render many range sites useless for cattle production by displacing
valuable forage. Grazing capacities for livestock can be reduced 65% to
90% from the original productivity. Currently, weeds cost farmers over
$100 million each year in expenses and crop production losses in
Montana.
Can noxious weeds displace native plant species?
Yes. Noxious weeds out compete most native
plants for soil nutrients and soil. In Glacier National Park, spotted
knapweed reduced the frequency of six native species and totally
eliminated seven other rare and uncommon native species in a three year
period. Eleven native species were found adjacent to a leafy spurge
infestation, but only three native species remained inside the
infestation. The invasion of our range land by noxious weeds poses a
serious threat to the conservation of native plant communities.
Can noxious weeds lower plant diversity?
Yes. Plant diversity is needed to maintain
healthy plant communities that resist weed invasion. Many noxious weeds
such as Russian knapweed, leafy spurge, and spotted knapweed, reduce
plant diversity of native range land. Plant diversity is needed to
maintain the ecological integrity of the habitat, provide resistance to
weed invasion, and preserve genetic material necessary to adapt to
long-term changing and environmental factors. Plus, many people
agree that a diverse plant community is just more beautiful.
Can noxious weeds change the way a plant community works?
Yes. Each plant community has evolved certain
ways to cycle nutrients, cycle water, capture energy from sunlight, and
store energy in a form useable by animals. Noxious weeds alter the way
these processes work. By increasing surface erosion, noxious weeds
cause a loss of organic matter and nutrients that are normally
concentrated in soil surface layers. The removal of organic matter also
reduces infiltration capacity, thereby making water less available for
plants. Because many noxious weeds have relatively sparse plant
canopies, more water evaporates from the soil surface, which makes even
less moisture available for plant growth.
Can noxious weeds increase soil erosion and soil sedimentation?
Yes. Protecting and conserving the surface
soil are critical to the long-term sustainability of healthy,
functioning ecosystems. Soil provides nutrients and moisture necessary
for plant growth and is fundamental to all life. When spotted knapweed
invades range land dominated by native bunch grass, protection of soil
and water resources is compromised. In one study, runoff was 1.5-times
higher and sediment was 3 times higher on spotted knapweed-dominated
plots than on plots dominated by the native bluebunch wheatgrass
(Montana's state grass). Loss of soil because of noxious weeds may have
very serious consequences in the future.
Can noxious weeds affect recreational value and uses?
Yes. For most recreationists, the enjoyment
of being outdoors in diminished in areas dominated by noxious weeds.
Riding horseback through houndstongue promotes husbandry problems for
horses when seeds attach to the hide. The invasion of spiny weeds, such
as Canada thistle and musk thistle, limits river access and the sharp
spines make walking difficult. Leafy spurge has a white sticky
sap that is an irritant to some people.
Noxious weeds that displace non game wildlife lower
the quality of the outdoor experience for many recreationalists.
Loss of habitat for game animals and fish decreases success of hunters
and anglers. This reduces the value to and the use of noxious weeds
infested areas by recreationists.
Can noxious weeds cost many Montana and people from other states
millions of dollars every year?
Yes. It has been estimated that the economic
impact of leafy spurge in Montana, North and South Dakota, and Wyoming
totals $ 129.5 million each year and may result in the loss of
1,433 jobs. In Montana alone, spotted knapweed is estimated to cost $42
million each year. If this weed is allowed to expand to its fullest
range, it could cost Montana's over $ 155 million each year.
Can noxious weeds reduce the value of land?
Yes. Knapweeds infestations have reduced the
appraised value of land in Oregon. On one $2 million recreational land
transaction, the purchase was reduced to $200,000 because of the level
of sulfur cinquefoil infestation. Realtors are seeing more potential
buyers scrutinize weed infestation and management practices before
closing. On production-oriented land, noxious weeds are usually
considered in land appraisals. In one analysis, the presence of a
noxious weeds that reduces carrying capacity by 60% lowered the value
of the land from the original $220 to $100 per acre. In
Montana realtors MUST by law disclose to the buyer if a property has
noxious weeds.
Are weeds as bad as a forest fire?
Yes. "Invasive weeds have been described as
a raging biological wildlife- out of control and spreading rapidly."
Millions of acres have been invaded or are at risk, including range
lands, forests, wilderness areas, national parks, recreation sites,
and wildlife management areas. And think about it, they do
now "go out" during the winter like fires do...
Do weed infestations spread?
Yes. They enlarge and spread very much like
wildfires. The seeds can be carried very far by wind or other means.
Are biological control agents
(insects) safe? Will they eat anything else besides the weed?
Many biological control agents are
ecological specialists. That means that they eat only one type of plant
(the weed!) and often even feed on only one part of one type of plant.
These agents have been rigorously scientifically tested to be sure that
they are species specific feeders (i.e. are safe) before import and
release.
What is the difference between a pesticide and a herbicide?
Pesticide is mixture of chemicals used for
preventing,
controlling, or lessening the damage caused by a pest (usually an
animal). Most pesticides
are poisonous to humans. An herbicide is used to kill specific types of
plants. Biocide is a word that covers all types of life killing
chemicals [fungicide kills fungus, etc.].
What is biological control?
"Biological control is the deliberate
introduction or
manipulation of a weed's natural enemies with the goal of suppressing a
weed's populations. A biological control agent can be a insect, a
fungus, a nematode, or any other organism that retards the weed's
growth and/or reproduction. Most biological control agents are imported
from the weed's country of origin. Biological control agents never
completely eradicate a weed from an area but can keep a weed population
below economic impact levels." (3)
Literature Cited
(1)
King County, Updated:
August 5, 2003, Noxious Weeds Control Program, 1 January 2008.
http://dnr.metrokc.gov/wlr/lands/weeds/faq.htm
(2)
Bureau of Land
Management's Weeds Website, unknown update and publish, FAQs, 1
January 2008.
http://www.blm.gov/weeds/FAQs/FAQs.htm
(3)
State of Idaho
Agriculture, unknown update and publish, Frequently Asked
Questions, 1 January 2008.
http://www.agri.state.id.us/Categories/PlantsInsects/NoxiousWeeds/FAQs.php#NWQ7
mtwow.org HOME
Updated by Mika Flynn
Tuesday, 19 February, 2008.