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Biological Control: Biological control is the use of insects or other natural predators to control the growth of a specific plant species. The insects usually come from the invasive plant's native habitat and all have been extensively tested to ensure that they will not attack plants other than the one they are targeting. Insects are available from private companies and once established, can often support their own growth and expansion. Different insects attack different parts of plants at different times, but over time may decrease seed production and growth rate.
Grazing: Grazing is the use of sheep, goats, cattle, or horses to control weed growth. Sheep and goats are most commonly used in this function because they often eat plants rejected by cattle and horses. Animals will eat plants at specific stages of the plants' growth, so it is important to be informed about what animal is the best agent at different times of the year. It is also very important to make sure the land is not over-grazed and that the animals are moved before they start to eat native plants, which would eliminate native plant competition with the invaders.
Herbicide: Although herbicides must be used with extreme care and caution, they are one of the most effective ways of quickly managing weed populations for the short term. When considering what herbicide to use, look at what weeds you have, how close you are to water, what time of year is best to apply the chemical, and whether you need to hire a certified herbicide applicator. Herbicides often work best if applied more than once and in conjunction with other control methods.
Hand-pulling: One of the most labor-intensive methods of weed management, hand-pulling is a viable option for small infestations. Hand-pulling does not work on plants with rhizonomous root systems because it will stimulate the plant's growth. Pulling is often best in the spring before the weeds have an extensive root system. Tools like the weed wrench greatly assist in pulling small bushes or plants with long taproots.
Mowing: Mowing can be effective in some situations if it is done at the correct time of the weed's growth cycle. However, mowing can stimulate many plants' growth. Additionally, mowing damages as many native plants as invasive and usually requires multiple field entries over a span of years to kill all the weeds. You generally will have to reseed after mowing, which is another step in a labor-intensive procedure. Nonetheless, used in conjunction with other methods, mowing can be an adequate option in a long-term plan.
Prescribed Burning: Some organizations often use prescribed fires to control noxious weeds. Some plants require fire to germinate, but fire can also reduce the numbers of some species. Prescribed fires are most useful for controlling invasive plants in the spring before flower or seed set or at the sapling stage. Please be advised that fires can potentially burn too hot, which harms the soil, and also that some invasive species respond to fires by increased reproduction. Please consult The Nature Conservancy's Fire Management & Research Program if you are considering using fire as part of your integrated weed management plan.
AN INTEGRATED APPROACH TO WEED MANAGEMENT
Information courtesy of Center for Invasive Plant Management
Montana Counties Noxious Weed List
Information courtesy of Montana Department of Agriculture
Category 1.
Category 1 noxious weeds are weeds that are currently established and generally widespread in many counties of the state. Management criteria include awareness and education, containment, and suppression of existing infestations and prevention of new infestations. These weeds are capable of rapid spread and render land unfit or greatly limit beneficial uses.
Canada Thistle (Cirsium arvense)
Field Bindweed (Convolvulus arvensis)
Whitetop or Hoary Cress (Cardaria draba)
Leafy Spurge (Euphorbia esula)
Russian Knapweed (Centaurea repens)
Spotted Knapweed (Centaurea maculosa)
Diffuse Knapweed (Centaurea diffusa)
Dalmation Toadflax (Linaria dalmatica)
St. Johnswort (Hypericum perforatum)
Sulfur (Erect) Cinquefoil (Potentilla recta)
Common Tansy (Tanacetum vulgare)
Ox-eye Daisy (Chrysanthemum leucanthemum L.)
Houndstongue (Cynoglossum officinale L.)
Yellow Toadflax (Linaria vulgaris)*
Category 2.
Category 2 noxious weeds have recently been introduced into the state or are rapidly spreading from their current infestation sites. These weeds are capable of rapid spread and invasion of lands, rendering lands unfit for beneficial uses. Management criteria includes awareness and education, monitoring and containment of known infestations and eradication where possible.
Dyers Woad (Isatis tinctoria)
Purple Loosestrife or Lythrum (Lythrum salicaria, L. virgatum, and any hybrid crosses thereof)
Tansy Ragwort (Senecio jacobea L.)
Meadow Hawkweed Complex (Hieracium pratense, H. floribundum, H. piloselloides)
Orange Hawkweed (Hieracium aurantiacum L.)
Tall Buttercup (Ranunculus acris L.)
Tamarisk [Saltcedar] (Tamarix spp.)*
Perennial pepperweed (Lepidium latifolium)*
Category 3.
Category 3 noxious weeds have not been detected in the state or may be found only in small, scattered, localized infestations. Management criteria includes awareness and education, early detection and immediate action to eradicate infestations. These weeds are known pests in nearby states and are capable of rapid spread and render land unfit for beneficial uses.
Yellow Starthistle (Centaurea solstitialis)
Common Crupina (Crupina vulgaris)
Rush Skeletonweed (Chondrilla juncea)
Eurasian watermilfoil (Myriophyllum spicatum)*
Yellow flag iris (Iris pseudacorus)*
When establishing an integrated weed management plan, the ultimate goal is to restore and maintain a healthy plant community. It may not be realistic to expect that your land will be totally weed-free, even after years of weed management. Instead, getting weeds under control, i.e., not spreading and not choking out native growth, is an outcome to strive for. Therefore, choose accordingly and realistically when deciding which methods to implement in your integrated weed management plan. For more detailed information about weed management procedures, please consult your state weed coordinator or county extension agent.
OFF SITE LINKS TO ADDITIONAL WEED INFORMATION
NOXIOUS WEED MANAGEMENT
One study estimates that the total costs of invasive species in the United States amount to more than $100 billion each year. Noxious weeds have effects across the board from tax dollars to reduced property value to destruction of wildlife grazing habitat.
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