"Fall is the perfect time to collect soil samples for testing. Detecting SCN in fields this fall will allow growers to develop management plans to combat the nematode before next season begins," he said. "If SCN numbers are not too high, SCN-resistant soybean varieties will work great for next year's crop."
Soil samples should consist of multiple soil cores collected with a soil probe. Fifteen to 20 soil cores, 6 to 8 inches deep, should be collected in a zigzag pattern from no more than 20 acres, and the cores should be mixed before being placed in a bag for submission. Several samples will need to be taken from large fields.
Harvested fields with corn stalks should be sampled to determine if SCN is present for next year's soybean crop. However, fields in which soybeans were grown in 2002 also can be sampled.
"It is more important to sample fields in which soybeans will be planted in 2003 to know whether SCN-resistant soybean varieties should be grown," Tylka added.
Soil samples can be analyzed for SCN by the Iowa State University Plant Disease Clinic. The fee per sample is $15 for samples from Iowa, $20 for out-of-state samples. Forms for submitting soil samples to the Iowa State Plant Disease Clinic can be obtained from any county extension office.
Tylka pointed out that many private soil fertility laboratories also offer SCN testing as a service. "Check with the private soil fertility laboratory you routinely use to see if they offer SCN analysis. Growers can use one soil sample for both soil fertility and SCN testing if sent to a laboratory that offers both services."
If SCN is discovered in a field this fall, there are many choices of SCN-resistant soybean varieties from which growers can choose for the next growing season. Most soybean seed companies have SCN-resistant soybean varieties, which generally are available with or without herbicide resistance. A listing of the SCN-resistant soybean varieties available for Iowa growers can be obtained or ordered from any county extension office.