Soybean cyst nematode co-evolved with crop

They are tiny world travellers and Manitoba’s Red River Valley could be 
the next stop on the soybean cyst nematode’s global tour

Mario Tenuta holds up a jar containing soybean roots with nematodes for inspection at the Ian N. Morrison research farm near Carman.

In the middle of the Ian N. Morrison research farm near Carman, an unlikely scene is unfolding as farmers and agronomists crowd around what looks like an old jam jar.

“Careful, we don’t want this to break,” Mario Tenuta stresses, with a bit of a chuckle.

But what’s inside the tightly sealed jar is no laughing matter. Hidden in a tangle of soybean roots is a tiny organism that has the potential to become soybean growers’ next nemesis should it be unleashed in Manitoba.

To date, no cases of soybean cyst nematode have been identified in the province, but the University of Manitoba soil ecologist said it’s only a matter of time before it arrives.

“My take-home message is that soybean cyst nematode is geared biologically to be with soybean and wherever we move soybean around the world, guess what… soybean cyst nematode will eventually follow, and that’s where we are today in Manitoba,” Tenuta told producers during Manitoba Pulse & Soybean Growers’ annual SMART Day late last month.

As soybeans developed in ancient China, so too did the nematode, he explained. And as soybeans moved beyond the Asian continent, the tiny pest went with it.

“They have co-evolved, folks, co-evolved to the point where the soybean cyst nematode really needs soybeans to survive,” the soil ecologist said.

On the move since 1954

First introduced to North America in the 1760s, soybeans were largely considered a forage crop until the time of the Great Depression when other uses were explored and promoted. The search for better production methods led to the importation of soil inoculum in the 1940s and ’50s, a move that likely stamped the nematode’s passport, ushering it onto North American soil. It was first officially identified in the Carolinas in 1954.

Today, soybean cyst nematode is present across the U.S., including in North Dakota. It’s also found across Ontario and in some areas of Quebec.

It can travel in soil, with birds, on plant material and in flood waters, making the Red River Valley a likely place for the soybean cyst nematode to appear, he said.

“It has been moving northward up the Red River Valley, and it’s really well documented. In North Dakota, they’ve followed the progression closely, and in the last 15 years it’s worked its way basically into all the soybean-growing areas,” said Tenuta. “Canada customs are tough to get through — they ask about liquor and they take my venison sausage… they do a really good job. But they really suck when it comes to keeping nematodes and other pathogens out of Canada, so the nematode will come over.”

Rauri Qually, who farms near Dacotah, said he’s “deeply” concerned about a possible incursion of nematodes following the presentation.

“It doesn’t sound like we have much of a defence against these things,” he said, but added that he’s still meticulous about biosecurity, washing all equipment before it moves to a new location.

Tenuta said that’s the right attitude, adding that producers should keep up biosecurity, making sure equipment coming onto and off the fields is free of soil, especially if it’s travelling between farms or across borders.

As for what the soybean cyst nematode actually does, Tenuta said it essentially hijacks the plant to create its own food factory.

“The nematode life cycle goes as follows: the female has died and she’s packed with eggs inside her, as that soybean root comes up close to that dead female, and she’s called a cyst at this point, the eggs are stimulated to hatch… then they migrate towards the root,” Tenuta said. “They poke a hole into the roots, gain entry into that root, and they just stick their head into the root and just start feeding.”

Presence of the nematode can reduce yields by as much as 20 to 30 per cent, and is often difficult to diagnose.

Rotation and resistant varieties

However, it can be managed by crop rotation and resistant varieties.

“And no, snow doesn’t count as crop rotation,” said Dennis Lange, a crop specialist with Manitoba Agriculture, Food and Rural Development.

He added that other edible beans and some weeds can also play host to the soybean cyst nematode.

Gil Martel of St. Leon has only grown soybean for a couple of years, but said the information was helpful, adding he’s going to take another look at his rotation schedule.

“It certainly gives you something to think about,” he said.

Producers will also have much to consider when it comes to variety selection, as even resistant varieties break down over time, losing their effectiveness.

“I encourage growers to use them, but it is a cat-and-mouse game,” Tenuta said. “Because if the soybean has restart genes, guess what? The nematode evolves.”

About the author


Shannon VanRaes is a journalist and photojournalist at the Manitoba Co-operator. She also writes a weekly urban affairs column for Metro Winnipeg, and has previously reported for the Winnipeg Sun, Outwords Magazine and the Portage Daily Graphic.



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