The Evolution of Weed Eradication

In preparation for the discussion of the Department of Public Work’s recommendations on spraying wild parsnip, I looked into the active ingredients and the variety of eradication methods. Councillor Dalgity also shared some Health Canada information about the product that he obtained. Online, I looked at many documents from sources charged with approval of pesticides such as Health Canada, the Ontario provincial government, the US Environmental Protection Agency, the European Union, and others that mentioned the active ingredients in Clearview. We heard from farmers, both those who use herbicides and organic, who invest a lot of money, time, and effort in their products and do not want them endangered. I received email from three people whose children were badly burned, and heard from a few others who suffered minor burns or had treated burns.

I will convey what I understand from all this:

Reference point: we are all required by law to eradicate noxious weeds under the Ontario Weed Control Act. After reading Ontario guides from different years, it looked to me like some plants are removed from their list and new ones are added. If a person has noxious weeds on their property, they could be ordered by a weed inspector to remove them. If they don’t, they will be removed anyway and the Municipality gets billed for the cost. The Municipality in turn recovers any cost on the property tax bill. Growing up in Manitoba with several big seed companies like McKenzie’s, that was not new to me.

The Province mandates the eradication. The federal government and Province approve the herbicides.

The product, Clearview, seems to be an improvement over older type herbicides which were much stronger, persisted longer and were more toxic to other life forms such as animals, insects, fish and humans. The earlier product recommended for Giant Hogweed and Wild Parnsip contained glycophates, which I understand are now in question. In the 2015 version of the Guide to Weed Control, a footnote said that test projects at the University of Guelph indicated that Clearview did well. Clearview is different in that it is not metabolized by anything but plants. Different things I read said that it dissipates quickly after spraying and will not remain for very long, except maybe in legumes like soybeans. Its minute application is very diluted with water.

The active ingredients are Aminopyralid Potassium and Metsulfuron-methyl. While some claim that Clearview has not been tested, the active ingredients have. Both were tested by the United States Office of Prevention, Pesticides Environmental Protection and Toxic Substances division and reviewed by a joint Canadian-American panel. The European Union also reviews the various ingredients of herbicides. All this information is easily found online. It is not true that only Dow tested the ingredients; there were quite a range of tests by various companies and organizations including International Wildlife, as cited in the US Environmental Protection papers.

The product instructions caution against repeated use to avoid plants building a resistance to it. If spraying is successful, Clearview should be needed less and less. This was borne out by recent City of Ottawa and Lanark County evaluations.

It is a balancing act: spraying will kill some other beneficial broadleaf plants, which can be slow to come back. However, the invasive weeds are already crowding out natural plants and infesting agricultural fields, causing pollinators like bees to lose some of their preferred sources. Farmers keep bees like livestock. Failure to control weeds on municipal property adds to the burden on our agricultural producers.

For the future, scientists are researching more specific and gentler herbicides but also insect predators that could be imported to prey on the wild parsnip. There was some success with importing two types of beetles from Europe to attack the purple loosestrife, although the beetles were reportedly picky about where they would work! Importing predators can be a double-edged sword if the insect predators then take on desirable plantlife.

We might expect to see it in use on wild parsnip. The insects used are parsnip web worms. They would also be a foreign species so caution is in order. I read an article about how the wild parnsip in New Zealand “let down its defences” after being separated from its predator for 100 years. The result was that wild parsnip was pretty much wiped out very quickly. Dr Coupland alluded to this information. The North American parsnip may not be as vulnerable.

I learned that even domestic parsnip can be irritating, although more mildly. I heard that there were 26 property-owners who opted out of spraying last year, and 20 of these controlled it on their own, by puling it out mostly. This year, concerned citizens can group together and Adopt-a-Road to eradicate the pest manually. Our Public Works can give you more information on opting out and adopting a road.

If people insist that all herbicides be banned, or think that wild parsnip should not even be controlled, they might lobby the provincial and federal governments with their evidence. We can’t change those laws here.

This Council was in favour of allowing opt-outs and encouraging Adopt-A-Road volunteers, but wants to be strictly vigilant in protecting people and animals from burns and agricultural resources, both traditional and organic, from invasive plants. We expect that the required conditions of spray application, such as buffers around water, will be strictly observed by the licensed operators. This is a balanced approach, tailored to local preferences, but keeping our Municipality absolutely within the law. We expect that those who opt out or adopt a road share this view.

The good news is that we are witnessing the evolution of dealing with invasive species using methods, including herbicides, with the least amount of impact on non-targets that is reasonably available right now. We have witnessed this approach before, in medicine. Manufacturers and governments are changing, thanks to the concern of people like the delegates who cautioned against spraying. Because of their concerns, the management of pests is evolving to include safer and more organic means in future I am sure.

If you do want to tackle the wild parsnip on your own, I heard at the February 23 Business Breakfast that Indian Creek Orchard Gardens of Pakenham will be offering workshops on the proper removal of wild parsnip.

Their website is here:

and you may email them about the workshops here:

For more information:

Dr Paula Stewart’s presentation from February 2018

Invasive Species website