As farmers move toward harvest it’s prime time to check soybean cyst nematode populations (SCN). The pests’ population is at its highest at the end of the season, which can help give farmers an idea of the extent of the issue or help farmers who’ve never had the pest before identify the problem.
“The five long-suffering SCN states are Ohio, Iowa, Illinois, Minnesota and Missouri,” says Greg Tylka, nematologist at Iowa State University. That doesn’t mean the pest isn’t starting to sneak into other geographies, however. North Dakota and other western Corn Belt states need to be mindful of the pest.
“It’s [SCN] is the most damaging in new fields because it has no natural enemies, so yield loss potential is really high,” Tylka says. “In our states [Iowa, Missouri] natural enemies build up to keep it in check a little.”
In North Dakota, a state that only recently found the pest, active management is needed to stop the pest from building populations as big as those in long-suffering states. Unlike other states, SCN resistance to genetics isn’t as widespread.
“While in general [genetic resistance 88788] doesn’t work in Iowa, it does work for North Dakota growers,” says Sam Markell, North Dakota State University extension plant pathologist and professor. “We’re asking farmers to take the test [to see if they have SCN]. The other problem we face is we have a lot of edible bean production, which is another host. Genetic resistance is probably the best and most reliable method.”
Farmers in states such as North Dakota, South Dakota, Montana and parts of Kansas might need to move SCN resistance ‘up’ in order of seed importance. It’s easier to keep low populations low rather than try to bring high populations under control.
Even if you don’t see symptoms of SCN in fields, consider soil samples.
“You can have up to 30% yield loss in the absence of symptoms,” says Kaitlyn Bissonnette, University of Missouri. “About 80% of the fields in Missouri have resistance to the pest.”
Knowing the extent of the threat potential is key to management. When pulling samples visit fields like you plant them, by management zone. Certain soil types and conditions increase the likelihood of the pest, such as sandy soil.
In addition, SCN and sudden death syndrome (SDS) often go hand-in-hand, where you see one, you’ll like see the other. SCN injures the plant early, which can leave it more susceptible for the Fusarium pathogen in SDS.
Follow best management practices. Whether farmers have SCN or not, following best management practices can help reduce risk of severe outbreaks in fields.
First, the SCN coalition, a group organized to help ‘beat’ the pest, says to use genetics with resistance. Right now there are two options PI 88788, which has resistance in some states, or Peking varieties.
“We want to see more Peking used every day,” Tylka says.
Next, look at other control options.
“Seed treatments add some control, but they don’t last the whole season,” Markell says. “Crop rotation is also really important.”
Corn is a non-host crop and can help decrease populations, and so can wheat. However, it’s still important to test fields after corn and before soybeans to know what SCN levels are still present. Tests cost about $1 to $2 per acre, but some state soybean checkoff programs are offering cost assistance. Talk with local checkoff programs to see what states are participating.
“Sample like you’re going to farm it, don’t cut it where you can’t plant [or quickly change planting or management techniques],” Markell says. “Use 20 core samples for every 20 acres by management zone. Certain areas could be high risk such as entryways, low spots and high pH soils.”
High pH fields should move to the top testing priorities. The pest seems to thrive in those conditions.
“The economics of testing make sense, if it’s $20 for a 20-core sample that represents 20 areas that’s $1 per acre,” Tylka says. “SCN has the potential to take one-plus bu. per acre, so $1 is such a minimal cost.”