Biocontrol: Uniting Invasive Species with Natural Enemies

Invasive aquatic plants like invasive Phragmites are challenging because they often have fewer natural enemies (e.g., herbivores) and can outcompete native plants. Their spread can outpace costly and labour-intensive physical methods of extraction and chemical controls are best used with caution around our waterways and natural spaces.

Biological control – or “biocontrol” – uses host-specific living organisms to help suppress a target weed in other words, biocontrol uses highly specific natural enemies to stop a target plant from growing. Development of biocontrol for invasive Phragmites began over 20 years ago in Europe in 1998, with assessments of Phragmites as an appropriate target and a search for candidate biocontrol agents. Two stem-boring moths from Europe – Archanara neurica and Lenisa geminipuncta – were selected and extensive host-range testing demonstrated that both moth species are safe and specific to invasive Phragmites. In April 2019, a petition to release the insects in Canada was approved by the Canadian Food Inspection Agency (CFIA).

• Find the answers to the most frequently asked questions we’ve received about biocontrol
• Biocontrol in Ontario – The Progress So Far

Biocontrol Partnership

Ducks Unlimited Canada’s partnership in the biocontrol introduction of beetles (Galerucella calmariensis and G. pusilla) to manage purple loosestrife — another destructive invasive plant — was a great Canadian conservation success story. This otherwise benign insect successfully reduced the plant’s population and serves as a model of successful partnerships for operational biological control.

Building on this experience, Ducks Unlimited Canada has supported the University of Toronto and Agriculture and Agri-Food Canada research program for biocontrol of invasive Phragmites since 2019. This has included several Mitacs funding partnerships, providing site/property access and on- site logistical support, and expertise to conduct unmanned aerial vehicle (UAV) flights to help monitor field sites.

Phragmites biocontrol is safe

Modern biocontrol agents undergo extensive study and host-range testing to ensure that they only eat their target and will not affect other species. For the Phragmites moths, over a decade of testing was conducted by an international research team from Switzerland, Canada and the USA before they were approved for release in 2019 by the Canadian Food Inspection Agency.

Biological control is cost-effective, scalable and works with other management tools.

Conventional management tools – such as herbicides and manual removal – need repeated efforts over several years to suppress invasive Phragmites. This process is labour intensive and cost prohibitive on the continent-wide scale of Phragmites invasion. In contrast, biocontrol agents generally only need to be released at a site once, after which they will reproduce and disperse independently. This makes biocontrol a highly cost-effective, scalable, and long-term management strategy. While not a “silver bullet”, biocontrol can be used alongside other management tools to effectively manage Phragmites across Canada.