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Pest Patrol: Sanitation of weed seed

#PestPatrol with Mike Cowbrough, OMAFRA

Q: Can we stop the spread of weed seeds?

A: “I’ve been thinking a lot about sterility lately.” I knew as soon as the words came out of my mouth that I had slipped up. I was responding to a question in the audience at a local crop conference about ways to stop the movement of unwanted weed seeds into fields. I meant to say “sanitation” but it was too late. The audience was already wondering whether I had just made a big reveal about my personal life.

Sanitation has occupied my head space lately because I’ve experienced instances where the movement of weed seeds from species that are either herbicide resistant or difficult to control can happen easily. Although it would be easy to shrug and say “that’s why they’re weeds,” we should be looking for practical and effective solutions to stop seed spread, especially when species like Palmer amaranth, which we don’t have in Ontario, have proven to be a real production challenge in parts of the United States and could very easily be introduced via seed contaminating grain loads, farm machinery and transportation vehicles. So what can be done?

Weed seeds collected inside my boot after walking in a field.
photo: Supplied

Legislation: Many provinces in Canada do have “noxious weed” legislation (full disclosure: I administer Ontario’s Weed Control Act). Although I think weed control acts serve as a foundational piece that can provide a bit of muscle when landowners flat out refuse to control noxious weeds, if they are the only mechanism to prevent the spread of weeds, then success is unlikely. Often enforcement of weed control acts is reactive instead of proactive, which is not a criticism but rather the reality of most individuals employed to do weed inspection. Inspectors are tasked with a number of other by-law enforcement activities. There are not enough resources to do proactive management of noxious weeds, and with a large list of infrastructure needs in many areas, my guess is that minimizing the movement of weed seeds is not at the top of the priority list. You could, however, pare down the noxious weed list to only species that are herbicide resistant (for example), providing a much narrower (and attainable) goal for enforcement by weed inspectors. Even then, the cost of implementing proactive roadside weed control would be high. For example, in Maryland it was estimated that state costs to manage Palmer amaranth would be around $3 million and this did not include the cost to re-establish programs that were discontinued in nine counties.

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Heat: With enough time and a high enough temperature, the viability of weed seeds can be destroyed. It’s a lot like comparing food preparation with a microwave versus a slow cooker. One method can be done quickly but with high energy demands, while the other can be done with less energy but slowly. The sweet spot will have to be figured out. But could you put a combine in a room at 60 C to kill the viability of weed seeds that are hiding within that piece of machinery? How long would it take?

Liquid: Other than boiling water (see heat) there does not seem to be any magical solution that you could wash equipment with to kill weed seed, at least not according to my internet search browser. Likely, if a spray solution was effective at destroying the viability of a weed seed, my guess is it wouldn’t be gentle on the paint finish either.

The amount of seed collected from the inside of my boot after walking a field for a farmer. Four different species were found, one of which (pigweed) contained herbicide-resistant bio-types.
photo: Supplied

At this point I have more questions than answers, but with seemingly more herbicide-resistant weed species, it’s worth our effort. Drop me a line if you have any ideas that you think should be experimented with.

Have a question you want answered? Hashtag #PestPatrol on Twitter to @cowbrough or email Mike at [email protected].

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