A plant pathology specialist says harvest is the best time to get an accurate population count of soybean cyst nematodes (SCN). Soybean yield losses resulting from SCN have not been measured, but South Dakota State University’s Madalyn Shires told the South Dakota Soybean Network that soil samples tested so far indicate high numbers of the pest.
“I can tell that our populations, again as we’ve suspected over the last few years, they rose due to drought. So, this year, I’m betting and guessing that our populations have probably been able to get in a couple of extra cycles of reproduction due to the drought [and] heat that we have had the last few months,” said Shires. “I’m assuming that we will see losses but I don’t have any numbers so far.”
Shires recommends that SCN testing be done at harvest time.
“It can be done as early as mid-August and it can continue to be done until the ground freezes,” she said. “Once the ground freezes, we recommend not trying to sample again until mid-spring to early summer.”
The South Dakota Soybean Research and Promotion Council – the Soybean Checkoff – foots the bill for counting SCN populations and also covers the more involved HG testing, said Shires, which determines how nematode populations respond to known lines of resistance.
“We pull those plants out and rinse them and count the resulting number of cysts,” said Shires. “That number gives us a percentage and we’re able to determine what levels of resistance may or may not be in that field.”
Other issues this season include scattered reports of soybean sudden death syndrome in northern South Dakota where it stayed a little cooler into the growing season. Brown stem rot has been a minor issue, and because of drought the past couple of years, according to Shires, leaf spot diseases are at a minimum.
“White mold is a persistent issue,” she said. “I didn’t receive a ton of reports of it this year, but I do know that it was seen in isolated areas in the eastern half of the state.”
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