Story by Agriculture and Agri-Food Canada

Vegetable growers often use herbicides to control weeds that affect production and cause yield losses. However, some weeds can develop resistance to herbicides. Not only does this impede weed management and cause yield losses, it also duplicates costs from having to try multiple weed control strategies, such as buying herbicides and hiring workers to manually remove weeds. This is a major issue for vegetable growers in Ontario and Quebec where 19 cases of suspected herbicide resistance have been reported since 2016 alone. That is why scientists at Agriculture and Agri-Food Canada are studying this problem.

To start with, the team surveyed vegetable cropping systems in Ontario and Quebec to look at the occurrence and distribution of herbicide resistant weeds. Traditionally, identifying resistance in a weed sample took six months and involved growing and evaluating the plants in a greenhouse. But because these resistant weeds can spread quickly within fields and to adjacent farms, the scientists developed several genetic tests that can help them detect herbicide resistance much faster. These new tests provide results in only a few days, enabling experts to recommend alternative weed control strategies within the same growing season. These tests have already been shared with the provincial pest diagnostic lab in Quebec, and additional tests will be developed as needed.

The rapid proliferation and spread of herbicide resistant weeds affects the sustainability of field vegetable crop production in Canada, an industry that generated more than $1.7 billion in farm cash receipts in 2017. This research will help growers quickly detect resistant weeds and enable them to use alternative weed control strategies much earlier to protect their crops.

Saint-Jean-sur-Richelieu Research and Development Centre: Dr. Marie Josée Simard, Dr. Martin Laforest, Sylvain Fortin, Luc Marchand, Manon Bélanger (retired), Brahim Soufiane, and Katherine Bisaillon

Harrow Research and Development Centre: Dr. Robert Nurse, Kerry Bosveld

Pest Management Centre: Dr. Cezarina Kora

External Collaborator: Kristen Obeid (Ontario Ministry of Food and Rural Affairs)

This project is partly funded through Pesticide Risk Reduction at the Pest Management Centre.

For more information:

Laforest, M., B. Soufiane, K. Obeid, M-J, Simard, E. Page, and R.E. Nurse.  2017.  Acetyl-CoA carboxylase overexpression in herbicide resistant crabgrass (Digitaria sanguinalis).  Pest Management Science.  73:2227-2235.

Simard, M.-J., Laforest, M., Soufiane, B., Benoit, D.-L. and Tardif, F. 2018. Linuron resistant common ragweed (Ambrosia artemisiifolia) populations in Québec carrot fields: presence and distribution of target site and non-target site resistant biotypes. Can. J. Plant Science.  98: 345-352.

Taking on herbicide resistance, Agri-info Newsletter — October 2018.