Assessing efficacy of treatment programs to control invasive Phragmites in highway corridors of southwestern Ontario

Chow-Fraser, P., Marcaccio, J.V. and deBoer, J.
Highway Infrastructure Innovations Funding Program Publications
October 2018: HIIFP Project #2016-09


The invasive haplotype M of Phragmites australis originated in Europe and was introduced to the Atlantic coast in the 1800s. It eventually made its way to southwestern Ontario in the late 1940s. Since 2010, invasive Phragmites has greatly expanded into coastal and inland wetlands throughout all Great Lakes states and provinces, and has become firmly established in road corridors. Dense stands of Phragmites can be dangerous near roads as they create a fire hazard, block sight lines, and can compromise the structural integrity of roadways and infrastructure. The Ministry of Transportation of Ontario (MTO) developed a control strategy that involves use of glyphosate, a broad spectrum herbicide, to protect the infrastructure of MTO from this nuisance grass, and also to prevent further spread from highway corridors to adjacent natural heritage areas, watercourses and agricultural fields. Using the McMaster Invasive Phragmites Database (MIPD), we conducted a change-detection analysis between 2010 and 2015 GIS data to assess the effectiveness of the weed control program in roadway corridors that has been on-going since 2012. Except for the major expressway (i.e. 400-series highways), the extent of Phragmites on most of the treated roads decreased in areal cover by >95%; removal rates associated with the 400-series highways ranged from 80-85%. It is important to note that the amount of new growth on Hwy 401 and 402 equaled or exceeded what had been removed, resulting in a net increase in Phragmites in 2016, despite the treatment program.