Prairie soybean producers have dodged the devastation that the soybean cyst nematode can cause.
However, the soybean pest is already on Canada’s doorstep and it’s only a matter of time before it arrives
“It’s on the doorstep … and it’s been munching steadily up the Red River Valley (from North Dakota) for the past 10 or 15 years,” said Mario Tenuta, a soil scientist at the University of Manitoba.
“What we want to do in Manitoba with our soy growers is to be a bit more proactive. We know it’s going to come here, so what we’re saying is let’s start surveying. Let’s start looking for it … because we want to know when it’s here, we want to know where it is and that way our growers can start adapting an managing for its presence.”
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The soybean cyst nematode is a common pest in the United States.
Growers and researchers in Manitoba have been monitoring for it for several years.
Soil samples are the best way to confirm the pest’s presence.
They were initially conducted primarily in Manitoba’s Red River Valley, but the sample area has been widened recently to include fields in other productions areas such as Winkler, Carberry and Portage la Prairie.
“So far, we’re coming up with a blank, so that’s a good thing,” Tenuta said.
“But eventually it will come across the border, that’s for sure.”
The soybean cyst nematode is generally a more prominent concern in areas that have a long history of soybean production.
The expansion of soybean acres in Manitoba, is a recent phenomenon, but the nematode has been expanding its range in the U.S. for years.
Berlin Nelson, a plant pathologist from North Dakota State University, said the nematode is now the most prominent soybean pest in North Dakota.
“If you’re not familiar with this pest, you should be because if you grow soybeans, eventually it’s going to get up here,” Nelson told a recent Soils & Crops agronomy workshop hosted by the University of Saskatchewan.
He said the nematode’s prevalence increased in step with North Dakota’s expanded soybean acreage from 200,000 acres in the early 1980s to nearly six million by last year.
Nematode infestations became common in all parts of the state during that time.
Cold Canadian climates are not likely to deter the pest’s northerly migration, Nelson added.
“It does just fine in the northern climate,” he said.
“Many of our growers thought it wouldn’t do very well when it got up into North Dakota — into colder temperatures and colder soils — but just the opposite. It just loves it up there and it has adapted very well.”
The nematode is difficult to detect until its impact on production is obvious and damage is irreversible.
The pest is a microscopic worm that attacks the root system of host soybean plants.
Female nematodes feed in the root’s vascular tissue, then exit the root and produce a large number of eggs that are eventually fertilized by the male worm.
Mature females are visible to the naked eye, but yields are likely already being affected by that time.
The entire life cycle of the nematode can occur in fewer than four weeks, meaning several generations of eggs can be produced in a single growing season.
The number of eggs contained in a sample of soil in experimental plots in North Dakota increased tenfold during one growing season.
Soil samples taken in spring showed an egg count of 283 eggs per 100 cubic centimetres, while samples taken from the same plot in October or November showed egg levels exceeding 28,000.
“This is the reproductive potential of this nematode under ideal conditions,” Nelson said.
The symptoms of an infestation can be difficult to diagnose. They can range from stunting and yellowing to complete lack of living plants in severely infected fields under ideal conditions.
“In many areas where we’ve had soybean cyst nematode … people do not recognize that they have it unless they get a soil sample,” Nelson said.
“That’s what we found in North Dakota. People just don’t recognize it. They don’t get out there and soil sample, and then they pay a very dear penalty when that nematode decides that it is going to really yank the yield out of that field.”
Nelson said the key to managing the pest is to use resistant soybean cultivars.
Once established, the nematode can survive on other host plants, including edible beans. It can also survive for a long time in the soil, regardless of what crops are grown.
“That’s the whole idea of the cyst, is that it’s a resting structure that is designed to withstand the stress of being in the soil for a number of years without a host,” Tenuta said.
Nevertheless, rotations are critically important and can go a long way toward ensuring that the pest does not get established.
“Rotation is always part of the picture,” Tenuta said.
“If you’re doing monoculture soybean, you’re just allowing pressure for a disease to build up over time … so if you can provide disease breaks, then you can slow down the ramping of the pathogen or the pest.”
Tenuta said Manitoba Pulse and Soybean Growers has been proactive in monitoring for the pest and increasing awareness among producers.
Growers who think they have the pest in their fields can contact the association to receive additional information about testing and management.
Contact brian.cross@producer.com
