Invasive Species Awareness Week in Manitoba April 21-27, 2019
The Province of Manitoba has declared the last week of April as Invasive Species Awareness Week (C.C.S.M. c. I97). The Manitoba Weed Supervisors Association (MWSA) recognizes this week by highlighting just a few of the invasive plants considered to be a significant threat to the landscape of our province.
The MWSA is comprised of and represents Weed Supervisors who are individually employed by Weed Control Districts formed by one or more Municipalities. Weed Supervisors work under the authority of The Noxious Weeds Act of Manitoba (NWA). The NWA sets out requirements regarding various control or destruction measures for different plants. A comprehensive listing of noxious weeds is found in The Noxious Weeds Regulation, which contains schedules that rank plants according to their threat levels and specifies the areas of the province to which these levels apply. The Act requires that Tier 1 weeds, must be eradicated without conditions.
Weed Control Districts, first started in 1964, have developed programs to deal with invasive plants such as leafy spurge and red bartsia, which have managed to establish within Manitoba, causing severe agronomic and economic impacts.
Leafy spurge, an invasive perennial first recorded in Manitoba in 1911 is a serious pest of forage and grazing land. A study conducted in 2010 by the Rural Development Institute (Brandon) estimates that leafy spurge caused a staggering annual economic loss (direct and indirect costs) of approximately $40 million. There’s little doubt that these costs have risen significantly since then.
Red bartsia is another forage and pasture invader. It was first introduced to the Gimli area in the 1950's. The Interlake Weed Control District was formed in 1967, and throughout the ensuing years control measures were undertaken. Unfortunately, a truly effective control program was not initiated until 1999. By that time red bartsia had infested much of the Interlake region. Although the weed is now being controlled on roadsides, the cost is huge. In the 2018 season, a total of $176,849.20 was spent controlling the weed on the district’s rights-of-way. With the district’s total known red bartsia infestation at 1,768.5 miles (one side), extensive seed reserves in the soil, and seed viability in the nine year range, there is no easy, quick fix for this problem. With new infestations of red bartsia already appearing in other parts of Manitoba, it is imperative that all areas incorporate careful monitoring and aggressive control measures to prevent further outbreaks. As with any invader, the best control is to prevent its initial introduction.
Both leafy spurge and red bartsia are on Manitoba’s Noxious Weeds Act as are the follow two weeds which are Tier 1 weeds on the Act. Either of them could pose a greater threat to Manitoba landscapes.