Farmers love them not: AAFC researchers target invasive daisies with a natural ally

If you live in the northern reaches of our Prairies or among the mountains of southern British Columbia and Alberta, you’re probably familiar with the pretty white “flowers” that dot the roadsides and fields. This plant is called oxeye daisy (Leucanthemum vulgare), and what you may not know is it's actually an invasive species from Europe. While it may look harmless, this invasive weed has become a big agricultural problem, especially in western parts of Canada.

Oxeye daisy threatens to take over pastures, reducing the quality and amount of food available for livestock. It also affects the production of forage crops like timothy hay and alfalfa, which farmers rely on to feed their animals or produce seed.

Battling the daisy takeover, naturally

Controlling large patches of oxeye daisy is not easy. Herbicides and mowing are often ineffective, especially in natural pastures that are hard to reach with farm equipment. These methods can also harm native plant species, making the cure more damaging than the pest itself. Combining herbicides with fertilizers to boost the growth of desirable plants can help in managed fields, but more solutions are needed.

To tackle this issue, Lethbridge Research and Development Centre researcher Dr. Rosemarie De Clerck- Floate is leading a Canadian research team that includes collaborators from the Summerland and the Saskatoon Research and Development Centres, and expert input from researchers at the Centre for Agriculture and Bioscience International in Switzerland (CABI). They are exploring a natural solution called biocontrol, to help limit the spread and impact of oxeye daisy. Biocontrol is the use of living organisms (like insects, parasites and predators) to manage and control pests.

“It’s so important that we do everything we can to help producers safeguard their fields from invasive pests like oxeye daisy. Through our research, we aim to give farmers and ranchers one more tool in their toolbox to help reduce the damage caused by this invasive weed.”

- Dr. Rosemarie De Clerck-Floate, Research Scientist, Agriculture and Agri-Food Canada

Since 2008, seven insect species were studied as potential candidates for biocontrol of oxeye daisy. Currently, the Canadian research team is focusing their efforts on one particularly promising insect – a small moth from Europe called Dichrorampha aeratana. Feeding by the moth’s larvae, mainly within the stems of oxeye daisy, helps control the weed by weakening it and reducing its ability to reproduce and spread. The larvae also overwinter in the base of the plant’s stems before becoming adults in the spring to repeat the cycle of feeding damage within oxeye daisy patches.

Showdown: moth vs. daisy

When studying potential biocontrol solutions, it’s critical to ensure that the benefits outweigh any potential risks. Before introducing the moth to Canada, CABI researchers, with support from AAFC, conducted 10 years of testing (from 2011 to 2021). They studied how the moth interacted with 75 different plant species, including 33 native to North America. The results showed that the moth strongly prefers and survives best on oxeye daisy, without harming any other species.

Based on this research, the Canadian Food Inspection Agency approved the release of the moth, and in June 2023, Dr. De Clerck-Floate and her team released 850 moths—mostly larvae and a few adults—in three pasture fields: two in southern British Columbia and one in southwestern Alberta. These releases have shown the moth is able to survive – even in Alberta’s extreme winter temperatures, which can drop as low as -40°C.

The results are very promising, but it will take more research for this moth to reach its full potential as a tiny warrior in the battle against oxeye daisy. The research team is now working on ways to mass-rear the moths more efficiently, so they can be more available to producers and land managers, as part of an integrated pest management strategy.

Another step forward for producers

Dr. De Clerck-Floate and her team’s work represents a significant step toward protecting Canadian crops and fields from the spread of invasive species like oxeye daisy.

This important project is part of Canada's National Biological Control Program. Across the country, AAFC researchers are working together to develop biological control solutions for nine invasive insects and nearly 20 invasive weeds. This continued research is helping our farmers and ranchers protect their lands and livelihoods.

Key discoveries and benefits

• Oxeye daisy is an invasive weed that threatens to take over pastures and crops such as forage, reducing the quality and amount of food available for livestock and production of seed.
• Dr. Rosemarie De Clerck-Floate is leading a Canadian research team, exploring using a small European moth as a natural biocontrol solution to help limit the spread and impact of oxeye daisy.
• The results showed that the moth survives – even in the harsh Canadian climate – by consuming and living within oxeye daisy, without harming any other species.
• Dr. De Clerck-Floate and her team’s work represents a significant step toward protecting Canadian crops and fields from the spread of invasive species like oxeye daisy.

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Related information

• Lethbridge Research and Development Centre
• Dr. Rosemarie De Clerck-Floate
• Canada's National Biological Control Program