|
URBANDALE,
Iowa - Now that the skies have finally cleared and the state is drying out, soybean producers may have to deal with yet another potential yield-robber, the Soybean Cyst Nematode (SCN.)
Iowa State University Plant Pathologist Greg Tylka says SCN feeds on the soybean roots, which can cause significant yield loss even though SCN may not be visible.
“We’ve done research funded by the soybean checkoff that has shown you can have 40 percent yield loss occurring and the plants will not look sick above ground,” Tylka says. “Plants won’t look stunted or yellow, but you will surely find these little, white females on the roots.”
Tylka says to look for SCN during July and August, simply dig roots and carefully shake the soil away from the roots and look closely to see if any females are present.
“The other way to scout is to pull a soil sample and you can do that any time of year,” Tylka says.
Tylka also claims late planting may have helped growers when it comes to SCN.
“SCN completes its life cycle early in the season, even when the soils are cool,” Tylka says. “It may take five or six weeks for the life cycle to finish, but by midseason, it goes from once every three and a half weeks to four weeks. So, across the Midwest we typically would have three or four turns at the life cycle in a growing season. Since we’ve delayed our planting date in my fields by one month, there will likely be one less turn of the nematode cycle.”
Producers who weren’t held up by the rain will find females on the roots now, and depending on the weather, will have a normal amount of SCN reproduction this growing season. According to Tylka, SCN tend to thrive in hot, dry conditions.
“To grow SCN in a greenhouse, we keep plants very dry, almost to the point of wilting, before we water them again,” Tylka says. “For some reason, the nematode goes crazy in those hot, dry conditions. If a local field has cold or wet conditions, the nematode, even though it might do its normal life cycle as it would in any other year, doesn’t seem to thrive and produce as many eggs and cause as much damage as it would in a very hot, dry year.”
According to Tylka, finding SCN is not a death sentence for soybean production. There are many management options, but the best way is to keep low numbers low, instead of waiting until it’s a matter of driving high numbers down. To keep numbers low, SCN must be discovered early by scouting even before the top of the plant looks sick. Another way is to have a good crop rotation system.
To learn more, go to ISA’s Production Research Web page and on the left side under July, click to listen to the podcast entitled, “Effective Management Means Keeping Low Number of Nematodes Low.”
The Iowa Soybean Association
develops policies and programs that help farmers expand profit opportunities
while promoting environmentally sensitive production using the soybean
checkoff and other resources. The Association is governed by an elected
volunteer board of 21 farmers.
|
