While the soybean cyst nematode, Heterodera glycines, has yet to be found in Manitoba, producers are being urged to begin scouting now for what is sometimes called the “silent killer.”
“They call it the silent killer in areas where it’s been a problem for longer, because yield loss occurs long before symptoms are visible,” Holly Derksen told producers at St. Jean Farm Days.
Derksen, a field crop pathologist for Manitoba Agriculture Food and Rural Development, said that University of Manitoba researchers have been searching for signs of the disease — particularly in the Red River Valley — but have not yet identified any cases.
At the moment, the nematode’s range is expanding through North Dakota.
“So basically it’s moving north and we all know where we live, and we all know that the Red River comes this way, so chances are that it has moved to Manitoba, we just haven’t found it yet,” she said.
The nematode’s reach has also been expanding in areas of Minnesota and Ontario.
“So I say with caution that it’s not been detected in Manitoba yet,” Derksen said.
Because the soybean cyst nematode impacts plants before any symptoms appear, producers need to scout fields and examine plants even when they seem healthy, as yield will be affected before obvious signs of disease appear, the plant pathologist said.
If not, you may be left trying to get to the bottom of seemingly mysterious yield losses.
“So basically you’re losing yield and you don’t know why, you know what your plant count should be, but it’s not reaching that level,” Derksen said. “The first year, you’re probably chalking it up to abiotic stress or the weather… but eventually you’re going to start to figure out what’s going on, and then you’ll start to see symptoms.”
Once nematode infects the plant’s roots the female nematode will, over time, become a cyst. Later symptoms include chlorosis of the leaves and stems, suppression of root growth and root necrosis. But Derksen said farmers should aim to catch the infection at the cyst stage by digging up plants and inspecting the roots.
“So if you’re scouting for this, actually take a shovel, dig up the plant, carefully knock off the soil, then look for the cysts — and they’re tiny, so you might want to bring a magnifying glass,” she said. “And if you aren’t able to see them yourself, send them in.”
Resistant soybeans varieties are also available in Manitoba, and rotations of four to six years can help control cyst nematode.
However, because dry beans are susceptible to nematode as well, they cannot be used in a rotation meant to control nematode. Weeds like wild mustard can also host the disease.
But like any disease, it can only be managed once it’s identified.
“Knowledge is power, scout for diseases at low levels, you may think you have a beautiful crop and nothing is wrong, but you still need to get out there and make sure that you’re not missing anything that may be happening in the odd plant or patch, because you want to know what is there before you start to see these major yield losses,” Derksen said. “Also maintain those biosecurity practices, because those measures apply to all diseases.”