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War on weeds, take no prisoners

Hart Attacks: It will take money and commitment to just to hold enemy line

A waterhemp infestation can reduce soybean yields by 40 to 95 per cent.

A recent issue of the Manitoba’s provincial farm newspaper, the Manitoba Co-operator, carried some depressing news.

The province might be losing the war on herbicide resistant weeds; reports from the U.S. say despite some kind of trade deal with China, U.S. farmers figure they will need more than a $25 billion bailout in 2020 — (yes, that’s correct, more than $25 billion); and swine fever continues to spread through Poland, heading for Germany. I quit reading after that.

It must have been that late January blues that attracted me to those items. I know there are plenty of good things happening in agriculture, but those headlines seemed to gang up on my psyche.

I’ve often wondered about the war on weeds. There are plenty of great herbicides promising to be the solution to some of the most complex weed spectrum problems, and yet I don’t believe I’ve ever heard any farmer say, “thanks to herbicides we are seeing a lot less weeds in our fields.” (If that’s happening on your farm please let me know.)

In the Co-operator article written by editor Gord Gilmour, he talks to Tammy Jones, provincial weed specialist, about what she’s seeing out there. And it’s not all that pretty. With certain weeds, Mother Nature plays a tremendous numbers game.

Manitoba is dealing with a couple of new weeds that could become a threat for all Western provinces. As the Canola Council of Canada points out: “Tall waterhemp is confirmed in eastern Manitoba. Palmer amaranth is in North Dakota and moving north toward Manitoba and Saskatchewan. Both are big aggressive weeds with populations resistant to many herbicides, including glyphosate. If you find them, destroy them immediately.”

Jones is repeating that no nonsense message. Last summer she spent a few hours in a Manitoba field yanking about 300 well-rooted waterhemp plants from the ground and carrying them to the edge of the field to be destroyed. She estimates that effort removed about 90 million herbicide-resistant waterhemp seeds from the environment, helping to reduce the spread of one of the most aggressive weeds on the landscape.

She says that’s the type of vigilance farmers need to apply. If they see a small patch of weeds, whether it be this new waterhemp, or any other patch of weeds that seems to have survived a herbicide application, stop, get out, hand pull the weeds, remove them from the field and make sure they are destroyed.

Jones says it can cost money to apply proper control measures to remove waterhemp plants, but the alternative of doing nothing isn’t really an option. A waterhemp infestation can reduce soybean yields by 40 to 95 per cent.

And here’s where the numbers really mount up. One Manitoba farmer last year had a 35-acre patch of waterhemp weeds, resulting in zero crop yield over those acres. Not only did he lose about $9,000 worth of inputs spent to seed the crop on those acres, he then had to pull out all the stops to eradicate that large weed patch. With tillage and/or mowing and other measures, total cost of those weeds came to about $15,000.

Jones says it seems like a lot of money, but on the other hand that 35-acre weed patch had the potential of producing about 305 billion seeds. Even if normal control measures had eliminated 99 per cent of those weed seeds, that would have left a potential 300 million waterhemp plants. As Jones says, how can you grow any crop if you already have 300 million yield robbing seeds just waiting to take over?

It may seem like a losing battle, but researchers aren’t giving up. In Alberta, Breanne Tidemann, a weed scientist with Agriculture Canada in Lacombe, is urging Canadian farmers to consider some weed control measures that have been developed by Australian farmers. Chaff burning, chaff collection and removal, feeding chaff to livestock and installing weed-seed crushers on combines are some of the ideas being put forward. These measures aren’t necessarily winning the war on weeds, but they are helping farmers hold their ground on the battlefield.

About the author

Field Editor

Lee Hart

Lee Hart is editor of Cattleman’s Corner based in Calgary.



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