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Is the weed seed ‘destructor’ ready for prime time in Canada?

Aussie invention is much cheaper, easier to use, but is still in the ‘promising, not proven’ category

In the battle against herbicide-resistant weeds, the Harrington Seed Destructor might just win us the war — if farmers can justify the $100,000 price tag.

“If herbicides are still working, it can be hard to convince producers to spend that kind of money to purchase this kind of equipment,” said federal research scientist Breanne Tidemann.

“I think it’s going to be a hard sell just because it is a significant price tag.”

Developed in Australia in 2012 as a novel way to control herbicide-resistant weeds, the Harrington Seed Destructor generated some buzz when it first came to Canada in 2014. But it hasn’t gained much traction here in the five years since then.

The reason for that is twofold. First, the initial design was cumbersome — a heavy free-standing unit that towed behind the combine and crushed weed seeds during harvest. Second was the price of the unit, around $200,000.

But that’s changed in recent years, said Tidemann.

“As resistance increases and we need other options to control our weeds, we’re going to see more of these tools coming in.” – Breanne Tidemann.
photo: Supplied

The tow-behind unit has been scrapped in favour of a mill that can be integrated into the back of a combine, cutting the price tag in half and making it easier to use. Currently, there are three different mills on the market that can process the chaff coming out of the back of the combine, with more on the way (including one from Saskatoon-based Redekop Manufacturing, expected to be released in Canada next year).

“That improvement makes a huge difference in producers even being willing to look at it,” said Tidemann. “It’s a fast-developing industry, and they’re continually improving to try and make them even better. I wouldn’t say we’ve seen the final prototypes yet.”

And this type of harvest weed seed management is becoming increasingly important in a country that ranks behind only the U.S. and Australia for herbicide-resistant weed biotypes.

“Our resistance levels are continuing to increase as we continue to rely on herbicides,” said Tidemann. “As resistance increases and we need other options to control our weeds, we’re going to see more of these tools coming in. So we’re trying to promote this as a proactive way to get in front of it, and hopefully, your herbicides will last longer.”

Running out of options?

Wild oat resistance is a good example of what can happen if producers don’t get ahead of problem weeds, Tidemann added.

“It’s the most resistant weed in Western Canada right now.”

In the most recent Manitoba herbicide-resistance survey (done in 2016), federal researchers Hugh Beckie, Scott Shirriff and Julia Leeson found that in fields with wild oat populations, 78 per cent were resistant to Group 1 herbicide and 43 per cent were resistant to Group 2 herbicides.

Source: Manitoba Weed Survey, herbicide-resistant weeds, 2016.

But perhaps most alarming, wild oat populations resistant to both groups jumped to 43 per cent in 2016 (from 13 per cent in 2008 and eight per cent in 2002).

“When you have Group 1- and 2-resistant wild oats… there’s really only one herbicide left,” said Tidemann. “We’ve seen it happen in Australia. We’ve seen it happen in the U.S.

“If we keep relying on herbicides, we’ll keep selecting for more resistance, which means we’ll have fewer and fewer options.”

Mechanically crushing weed seeds could be the answer — and harvest is an optimum time to zero in on resistant ones.

“A lot of the weeds that we’re seeing in the field at the time of harvest are probably ones that already have a resistance profile to some of our in-crop herbicides. So preventing those resistant weed seeds from going into the seed bank and growing those resistant populations is a really good fit.”

Putting it to the test

But how well does mechanically crushing weed seeds work here?

Three years ago, Alberta provincial researchers started with stationary testing of the unit in a controlled environment, feeding chaff mixed with weed seeds into the seed destructor to see how the machine performed in the ‘lab.’

They looked at five different factors: species, seed size, seed numbers, chaff volume, and chaff type. All affected how well the machine worked but not by a lot — the machine lived up to its name, destroying (or at least sufficiently damaging) at least 95 per cent of weed seeds that passed through it.

“If you can get (the weed seeds) into the seed destructor, it’s going to work quite well,” said Tidemann. “It’s not 100 per cent control — there are things that will get through — but it does a really good job.”

Then it was off to the field to see how it worked in the real world. This time the researchers wanted to see what sort of impact it had on weed counts the following spring.

They targeted 20 fields in the Lacombe, Alta. area with a variety of crops and weed problems in the spring of 2017, marking out problem patches in the fields and then coming in with the seed destructor at harvest to compare the difference in weed control between it and a regular combine.

The results were mixed when weed counts were conducted the following spring, with no significant difference shown between the two treatments. That was to be expected in the first year of the study, said Tidemann, adding the 2019 weed counts were not yet available.

“Weeds have seed banks, so you don’t necessarily expect to see the full impact of that treatment in the first year,” she said.

“Even if you destroy 90 per cent of those seeds — which would be a very high proportion — you’ve still got a seed bank there that’s going to come up the next year. You have to do it a few years in a row to actually start driving that seed bank down.”

Out of the 20 fields in the study, only one field had a statistically significant difference in weed levels between the two treatments after the first year.

“Some of the fields had fewer weeds in the seed destructor treatment. Some of them had about the same. And one or two actually had more. But that’s not exactly an unexpected result one year after implementing these treatments.”

Integrated approach

So while it’s still too soon to tell whether the seed destructor will find a fit on Canadian farms, Tidemann is optimistic.

“I definitely think there’s some promise for it,” she said. “We would like to see producers using it before they’re developing resistance because it can prolong the life of their herbicides.”

But ultimately, the seed destructor is meant to be only one part of an integrated approach that’s “really season-wide,” said Tidemann.

“Harvest weed seed control is really your last kick at the can at the end of the season,” she said. “But if you’re using as many methods as you can throughout the season, hopefully you won’t have as many to deal with at the time of harvest.”

That means carefully managing weeds prior to seeding, establishing highly competitive crops, using in-crop herbicides properly, and adjusting your crop rotation to include other crop types, including winter annuals.

The alternative could be devastating, she added. Either weed control will become too expensive on farms with resistant weeds, or some farms will lose the ability to control these weeds altogether, leading to yield and quality losses and poorer grain prices.

“There are some people who don’t think we’ll end up as bad as Australia or the U.S., but we view Australia and the U.S. as the writing on the wall,” said Tidemann.

“Let’s not get to that point. Let’s try to change it before we get to that point.”

This article was originally published on the Alberta Farmer Express

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