Harvest is the perfect time to sample for the presence of soybean cyst nematode (SCN). Soil samples can be collected any time throughout the fall until a significant snowfall or hard freeze occurs.
Iowa State University plant pathologist Greg Tylka says it's a good idea to pull SCN soil samples every two to four years. "Growers should sample even if they know they have SCN and have been using resistant varieties. It's important to know what egg counts are and whether they are building despite the use of resistant varieties,” says Tylka.
For fall sampling, it is typically recommend to pull SCN soil samples from corn fields where soybeans will be grown the following year. However, you may also want to sample fields where you've noticed unusual plant growth during the season or unexplained low yields. One set of soil cores can be collected for both soil fertility and SCN testing.
Areas influenced by flood waters may need some special attention too. "Late, wet conditions typically do not favor SCN,” says Tylka. "That's the good news. The other side of that is floods move soil and you may want to test just to see what you are working with now.”