Noxious Weed Program

Looking for unwanted plant invaders started soon after settlers came to Saskatchewan with a few seeds of their favourite plants from far away lands. While many were beneficial, some of these plants came to dominate crops, pastures and native areas and now cause serious economic and environmental harm. These invasive plants are also called weeds and are not wanted by agricultural or environmental land managers.

Figure 1: Leafy spurge – A noxious weed and an invasive alien species.

In Saskatchewan , the worst weeds are declared noxious under the Noxious Weed Act. Section 13 (1) of the Act states: “Every owner or occupant of land shall destroy noxious weeds on his land and prevent the spread of noxious weeds to other lands.”

The Act, which has been in force in the province since 1909, empowers municipal governments to enforce noxious weed control by appointing a Weed Inspector as their enforcement agent.

Two important duties of a Weed Inspector are to enforce noxious weed control by private land owners and to prevent noxious weeds from spreading to new sites.

Among the weeds declared noxious under the Noxious Weed Act, leafy spurge (Euphorbia esula) is one that poses a serious threat of invading pastures and permanent grasslands. Leafy spurge (left) is a long lived, deep-rooted perennial plant that was introduced into Canada from Europe, and is now established in Saskatchewan and continues to spread.

In 1999, Thorpe and Godwin published Threats to Biodiversity in Saskatchewan, which examined the problem of exotic species invasion. From this report emerged Caring for Natural Environments: A Biodiversity Action Plan for Saskatchewan ’s Future (2004 to 2009) as a government-wide strategy to preserve the province's natural biodiversity. Invasive exotic species are animals, plants and other organisms that are not native to North America, Canada, Saskatchewan, or a particular natural environment. When introduced to a new area, they cause economic, environmental harm, and/or harm to human health. They can also be called Invasive Alien Species or Noxious Weeds (plants). Objective 5.4 of the Biodiversity Action Plan states: “Identify and introduce measures to control populations of invasive exotic species existing in the province.” Both documents identified invasive exotic species as a threat to biodiversity, and name leafy spurge as an example of an invasive exotic plant.

In Part Two, Section C (Environment) of the Federal-Provincial-Territorial Framework Agreement On Agricultural And Agri-Food Policy For The Twenty-First Century, there is agreement among federal and provincial governments that recognizes pest and biodiversity management. Two common environmental goals in the agreement are to “increase the use of beneficial pest and pesticide management practices” and “… promote compatibility between agriculture and biodiversity … .” For dominating, aggressive plants like leafy spurge, this is difficult, but can be addressed in an agri-environmental farm plan by using integrated weed control to prevent spread to agricultural and environmentally-sensitive land.  

Greater movement of materials, particularly grain and hay transport, has increased the opportunity for “hitch-hiking” weed seeds to drop to establish new infestations on road right-of-ways. Eradicating weeds early is better, both economically and environmentally, than waiting until they establish.

A leafy spurge seed can colonize a small area along a roadside in as little as four years, before it aggressively moves into the adjacent pasture or native plant communities. Horizontal roots spread the patch about 0.5 metres (m) per year and viable seed can be catapulted up to 4.6 m from an established stand to new areas, by seed pods that pop violently when mature. Human activities move the weed even faster, moving weeds great distances in one event!

Figure 2: Solid line indicates small initial patch of leafy spurge and dotted line indicates extent of additional second year plants resulting from seed spread when seed pods in initial patch erupt in a breeze. The drain in the foreground represents a risk of seed spreading greater distances in the drainage system. This seed spread could have been prevented by treating the small initial patch soon after establishment.

Leafy spurge is very competitive with range and pasture resources in Saskatchewan . When leafy spurge makes up 80 per cent of the vegetation cover, all grazing by cattle is eliminated because leafy spurge has replaced the grass cover. Cattle cannot eat leafy spurge due to the irritating, and toxic on rare occasions, sap that circulates through the entire leafy spurge plant. Make no mistake: leafy spurge is a dreaded plant invader! Eradicating the initial patch of leafy spurge is much more cost effective and requires less time and effort than trying to control an infestation once it is well established.

The Noxious Weed Program was started in 1999 to stop the spread of scentless chamomile, leafy spurge and other weeds because weed spread is such a threat to agriculture. The program targets weed inspectors, municipalities and landowners in the province.

The Noxious Weed Program promotes integrated weed control, which is a combination of non-conflicting control methods. Methods that can be integrated fit into the following categories: Physical, Chemical, Biological And Ecological. Physical control is manual pulling of weeds or mechanical removal of top growth by mowing. Chemical control is using herbicide to control or kill the weed. Classical biological control uses insects to attack and suppress a weed population and reduce its overall impact, but not eliminate the weed completely. Ecological control uses other desirable, yet competitive, plants to aggressively compete with weeds, or uses animals to graze weeds. The methods can be used at the same time or in sequence, depending on what has the greatest effect on the weed the least impact on the environment and the bank account.

The approach that local communities use to prevent weed spread should include all elements of Awareness, Education and Control of the weeds they are concerned about.

Awareness involves experts in the area of invasive plants and noxious weeds, providing information to weed inspectors and the public of the danger of new and noxious weeds. An important part of awareness is weed identification. Education involves learning about the biology, ecology and control of the weeds you are aware of. Control is the integration of Biological, Chemical, Ecological and/or Physical methods discussed above to achieve the best results. The challenge is selecting the best method or combination of control methods.

Strategies used to prevent weed spread at the individual or community level should include elements of Exclusion, Eradication and Containment. Exclusion involves the use of quarantine to keep new and noxious weeds at far away locations. Knowing the contents of that seed lot or hay bale from outside the municipality, province or country is key to excluding new weeds. Eradication is the reduction of a population of weeds to zero. The best opportunity to attempt eradication is when an invader first arrives and occupies a small area on road right-of-ways. Use the best herbicide available. Remember, herbicide residue can be beneficial in non-crop areas, except when there is a risk of environmental damage. Herbicide residues help to prevent the regrowth of weeds, but if used in environmentally sensitive areas, such as sandy soils or a high water table, herbicide residues are a brutal enemy! Once a weed becomes established, it is no longer economical or possible to eradicate, and weed control moves into the “containment” phase.

Figure 3: This is when eradication should be used for leafy spurge.

Containment means keeping a weed population within a specific area. Public awareness allows weed inspectors and landowners to quarantine areas with known invaders. Should eradication of a new weed fail, move on to develop a containment program to prevent spread of the weed. Containment is usually establishing a boundary, beyond which the weed will not be allowed to move. Inside that boundary, integrated management methods are used to reduce the overall impact of the weed and to reduce the opportunity for reproductive parts to spread.

Figure 4: This is when leafy spurge should be aggressively contained and controlled within the containment area (arrow shows the direction of leafy spurge movement).

The procedure to control a weed to prevent spread involves 1) scouting for a weed, 2) controlling the weed using integrated weed control and 3) monitoring for success. Marking the location of a known invader site as a waypoint in a GPS receiver has greatly enhanced the procedure to control weeds. Figure 3 shows a fairly new patch of leafy spurge that is colonizing and should be eradicated. This is not easy, because some seed may have been catapulted from the site and seed can remain viable in the soil for at least eight years. Figure 4 shows leafy spurge aggressively moving in the direction of the arrow. This weed population should be contained before it can spread further.

Figure 4 shows leafy spurge aggressively moving in the direction of the arrow. This weed population should be contained before it can spread further.

Through the Noxious Weed Program in Saskatchewan, weed inspectors are encouraged to aggressively eradicate small patches of leafy spurge (Figure 3) and other noxious weeds, and contain established weeds within large areas (Figure 4).

References

Anonymous. 2003. Federal-Provincial-Territorial Framework Agreement on Agricultural and Agri-Food Policy for the Twenty-First Century Part Two - Chapter Components of the Framework Agreement Section C – Environment. http://www.agr.gc.ca/puttingcanadafirst

Government of Saskatchewan. Date unknown. Caring for Natural Environments: A Biodiversity Action Plan for Saskatchewan’s Future 2004-2009.

Thorpe, J. and B. Godwin. 1999. Threats to Biodiversity in Saskatchewan. SRC Publication No. 11158-1C99.

Government of Saskatchewan. 1984. The Noxious Weed Act, 1984 . Available from Queen’s Printer, Province of Saskatchewan .

Dr. Garry Bowes is the Coordinator of the Noxious Weed Program ( phone 306.933.7695, fax 306.933.7352, e-mail gbowes@agr.gov.sk.ca. Financial support for the Noxious Weed Program has been provided by the Canadian Adaptation and Rural Development Fund in Saskatchewan (CARDS) and Agriculture Development Fund (ADF) to Saskatchewan Association of Rural Municipalities (SARM) in collaboration with Saskatchewan Agriculture and Food (SAF). Funding for the CARDS program is provided by Agriculture and Agri-Food Canada .

Weed Inspectors
Map of Weed Inspector Appointments - Current Year
Map of Weed Inspector Appointments - Previous Year
Noxious Weeds Act
Noxious Weeds Designation Regulations (Weed List)
Noxious Weeds Regulations (Order and Agreement Forms)