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Ontario Grain Farmer Magazine is the flagship publication of Grain Farmers of Ontario and a source of information for our province’s grain farmers. 

Understanding the Weed Control Act


every year, weed inspectors from across the province gather for the Annual Weed Inspector’s Conference. Weed Specialist Mike Cowbrough, from the Ontario Ministry of Agriculture and Food (OMAF) hosted this year’s event. On the agenda: weed issues affecting the agricultural community, new tools for keeping track of invasive species, and a brief review of the Weed   Control Act and enforcement cases surrounding it.


The primary objective of the Weed Control Act is to stop difficult to control weeds from establishing in agricultural fields. On the top of the list of challenges are concerns about glyphosate-resistant weeds, particularly in field crops. Some will see yield losses as high as 80-90 percent.

“The significance of this is that there are very few other herbicide options that we have available to control glyphosate-resistant giant ragweed,” says Cowbrough. “One option is to explore new technologies, or you go back to old school methods – hoeing, pulling.”

In the US Midwest, they are dealing with a species called Palmer amaranth, which is resistant to about five different herbicide groups. Producers have had to resort to pulling and hoeing. The species is very prolific as one plant can produce several kilograms of seeds – hundreds of thousands of seeds.

challenges with the act
One of the big challenges for field crop producers in Ontario today, has to do with the boundaries by which the Act is enforced on certain species. These boundaries are based on biology.

Take Canada fleabane, for instance. It’s a winter annual species and non-noxious. “You can find it throughout southern Ontario and parts of northern Ontario, it grows to five or six feet, produces a lot of seeds and is quite competitive,” says Cowbrough. “It has spread from a few locations in Essex County in 2009 to where we are today in 2013. What started off as four sites now has 155 sites. Why is that? Because it’s a windborne species that travels several meters.”

To understand how common ragweed spreads, for instance, you have to look at the pollen. Seeds travel as far as 100 kilometres away from the first plant. The more seed you produce, the more likely you are going to select for resistant weeds – and the more likely that resistant weed is going to spread.

“That’s a game changer in terms of how you enforce the Act, right? Section 22: The Act doesn’t apply as long as it’s not impacting negatively on agricultural and horticultural land. So what’s the impact of glyphosate-resistant ragweed found in the middle of Hamilton, say?” asks Cowbrough.

“The powers of enforcement start to become much broader than maybe what you’ve currently looked at. That’s my main point with the major agricultural issues right now. It’s glyphosate resistance. It’s ragweed species. It’s a noxious weed under the Act. I think we can probably stand to be a bit more liberal with how we enforce that and there’s good biology to support that.”

The second objective of the Act is to eliminate plants that are a host to either diseases or insects that affect the quality and production of food. European Buckthorn, for example, which can be found just about anywhere, is a host to stem rust in oats. “It’s also a host to other pests, like soybean aphid, which are tremendously detrimental to soybean yields,” says Cowbrough.

The last main objective of the Act is to reduce the risk of plants that are poisonous; particularly those that cause skin irritations, dermatitis, or are poisonous if consumed by livestock.

“How each weed inspector is able to perform his or her job is very unique to the region they cover,” says Cowbrough. The agricultural community, he says, is pretty clear when it comes to noxious weeds, though. They don’t want them anywhere near their property.

new identification tools

OMAF is working on making identification easier for producers. “We’ve made dramatic changes to the noxious weed section in the manual,” says Cowbrough. “It’s now clearer and there’s also a mobile web application for identification called”

Another web application was introduced at this year’s conference as well. Dave Copplestone of the Ministry of Natural Resources unveiled the EDD Maps tool or Early Detection Mapping System, a project that is a collaboration of the Ministry of Natural Resources, the Invasive Species Centre, and the Ontario Federation of Anglers and Hunters. The project is part of the Invasive Species Strategic Plan for Ontario, which places priority on recording systems, among other things.

EDD Maps will help farmers stay on top of the spread of invasive species by providing in-depth information and clear images of specific species. It also allows users to report sightings, should they find an unwanted species on their land.

“The goal of the system is to improve data collection and sharing,” says Copplestone. “And to assist resource managers with prioritizing efforts on the ground. It also builds capacity for invasive species reporting, so it will make it easier for resource professionals and the public to report sightings of invasive species. And it will help show us where species are spreading across the province.”

To check out EDD Maps, visit: •


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