Undesirable plants, or plants growing in locations that are not consistent with the land use objectives, are referred to as weeds. Weeds have an economic, ecological, and aesthetic implication on BCs grasslands. Weed management is developing a response to weed infestations or to prevent weed encroachment of currently weed-free communities.
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Definition of Weeds
Noxious weeds are usually non-native species introduced to BC through human activities. The BC Weed Control Act and its regulations require control of noxious weeds. Invasive species are non-native plants that have been introduced to an area where their natural controlling agents such as insect predators and plant pathogens do not occur. They are aggressive and have the ability to spread and thrive. Invasive plants are undesirable to humans either because they have no obvious beneficial qualities or because they interfere with our land management objectives.
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Effects of Weeds
Many hectares of native plant communities in BC have been overtaken by plant species that are referred to as invasive. Knapweed is an invasive weed of considerable concern with respect to BC’s grasslands. Both spotted and diffuse knapweed are highly competitive and capable of invading grassland sites to the exclusion of native vegetation. Knapweed species have been causing major environmental deterioration and reduced forage production in BC’s Southern Interior for more than 50 years.
Weeds are responsible for reductions in forage yield and quality and lead to ecological degradation through modification of plant communities and destruction of animal habitat. To the ranching industry, the economic impact of weeds on grasslands is a sum of the direct losses associated with reduced forage yield and quality, animal performance and stocking rate, plus the costs incurred in managing or controlling the infestation.
Weed Control
Weeds become established from improper grazing practices weakening the plants, soils disturbance arising from motorized and non-motorized vehicles, and dispersal of seed from humans and animals.
Weed control requires a high level of management. Ideally, the resource is managed to prevent weeds from invading. Once weeds are established, an approach potentially using a variety of tools may be required to eliminate the infestation or control its spread. Cultural and mechanical control, which include cultivation and mowing, are not generally feasible on natural grasslands. Manual control, such as hand pulling, can be very effective for small areas, but generally impractical on large scale grassland ecosystems. Biological control is commonly thought of in terms of the effect specific insects have on noxious weeds, such as Urophora flies on knapweeds. Chemical control with herbicides has been conducted on BC grasslands since the 1950s. Some herbicides are effective in the selective control of broad-leafed plants, including knapweeds.
Integrated weed management includes techniques that focus on prevention rather than eradication. Integrated weed management must be an essential part of the ongoing maintenance program for any property. This strategy is a balanced approach to resource management and must include the following processes for long term results:
To find out more, visit our Invasive Plant Resources page.
For more on grassland managment, visit the following links.
Grazing Practices
Ecological System
Research and Education
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