Rooting Out the Invaders: non-native plants
Common tansy ( Tanacetum vulgare ) © National Botanical Services / Erich Haber
Canada thistle ( Cirsium arvense ) © Parks Canada / YNP Slide 5c (7)
( Linaria vulgaris ) © National Botanical Services / Erich Haber
Non-native plants pose a significant ecological threat to native plant and wildlife communities because their natural insect predators and diseases are absent from areas they invade. Non-native or exotic plants displace native plant species that stabilize soils and provide forage and cover for wildlife. Lacking natural controls, non-native plants can spread rapidly, degrading wildlife habitat.
As many as 119 non-native plant species are found within Banff, Kootenay and Yoho National Parks. Canada thistle, common toadflax, leafy spurge, tall buttercup, tansy, and spotted knapweed are just some of the species of particular concern. These weeds are invasive, aggressive and spread at a rapid rate.
Weed Control in Banff, Kootenay and Yoho National Parks
Parks Canada has adopted a non-native plant control program called integrated pest management . The goal of this program is to prevent the introduction of non-native plants and to eliminate or control them, where practical, to maintain native plant and animal diversity.
Fighting the Weeds
Even though it's much more effective to prevent the introduction of non-native weeds into national parks, once established, non-native plants must be eliminated or prevented from spreading further. Several means of plant control are used as part of an integrated pest management program:
Hand pulling, mowing and string trimming (weed whacker) are mechanical methods for removing non-native weeds. Hand pulling is labour intensive and is best used for small infested areas. It should be conducted in the spring when the root systems of plants are weak. Mowing and string trimming are better used for larger areas. Both of these methods must be used before the non-native plants form seed heads.
Biological control has been used in areas in Canada and the United States. Research shows promising results for the viability of using exotic insect species or bio-agents, such as beetles and flies that feed selectively on non-native plants. Domestic goats and sheep have also been used to control non-native plants.
At this time, biological control method have been used on provincial lands adjacent to Kootenay National Park (Stoddart Creek area) and are being considered as another tool for the National Park weed control program. The use of domestic goats and sheep to control weeds inside national parks is not feasible due to the risks of introducing disease to native wildlife.
Herbicides provide another alternative to non-native plant control. Many herbicides are selective; they kill plants belonging to one group of plants while not harming plants belonging to another group.
Herbicides such as Milestone, Transline, 2,4-D and clopyralid may be used to target high priority, noxious weeds at specific locations of concern within National Parks. Noxious weeds are those that present a serious risk to the native plant and wildlife community. In most cases, herbicides will only be used to selectively reduce targeted noxious weed populations to a size small enough for mechanical control methods to successfully work.
The following methods will be applied in Banff, Kootenay and Yoho National Parks to control non-native weeds in both frontcountry (road accessible) and backcountry areas:
- Weed free hay is used for government ranches and backcountry warden cabin pastures.
- The brochure "Exotic Plants and Cultivated Landscapes in the Mountain National Parks: a growing concern" will be distributed to leaseholders and park residents to provide recommendations about which plants should or should not be grown in gardens within the national parks.
- Hand picking efforts will focus on several small sites within Banff, Kootenay and Yoho National Parks.
- A herbicide application program will be implemented. Specific herbicides and targeted areas include the use of Transline for treating Canada thistle sites in Lake Louise townsite and the use of Transline to treat Knapweed infestations in Kootenay National Park.
- A herbicide control program will also be discussed with Canadian Pacific Railway (CPR) to control or eradicate "butter and eggs" or toadflax from the CPR right-of-way in Banff and Yoho National Parks.
- Non-native plant inventories will be maintained and control sites will be monitored to evaluate the effectiveness of the program.
- Re-seeding of native vegetation will take place in areas that have been subject to weed control within the Lake Louise and Field townsites.
What can you do to help fight weeds?
- Learn to identify invasive, non-native plants and report infestations in the National Parks to the Warden Service.
- If you travel with pack horses, carry only weed-free forage into the backcountry. Ensure horses are clean of weed seeds before entering the backcountry. (poop through)
- Avoid traveling and camping in weed infested areas to prevent weed seeds from spreading.
- Backcountry roads adjacent to national parks are also vectors that allow non-native plants to spread in remote areas. Wash your vehicle often if you travel these roads as seeds can be spread from one area to another through the mud and debris on your vehicle.
- If you are a landowner outside parks, be responsible for controlling invasive, non-native plants on your property. The threat to native plant and animal diversity by invading non-native plants is not confined to National Park ecosystems.