This fall, the Iowa State University Plant Disease Clinic began using a new technique that increases the efficiency of extracting eggs from soil samples infested with the soybean cyst nematode (SCN). SCN egg counts from soil samples processed with this technique will be 100 to 200 percent greater than in the past. For example, a soil sample with a reported density of 1,585 eggs per 100 cm3 of soil with the previous technique now will have an egg density of 4,225 eggs per 100 cm3 of soil.

Because of the substantial difference in the number of eggs recovered with the two techniques, a direct comparison of the results of samples from the ISU Plant Disease Clinic with results obtained from the Clinic in the past cannot be made. It is very important for individuals who are monitoring their SCN population densities to not interpret increases in egg densities from samples submitted this year relative to samples from prior years as a true increase in nematode population densities. The management recommendations and egg population density classifications reported by the ISU Plant Disease Clinic have been adjusted appropriately to account for the increase in effectiveness of the extraction technique.

A notice explaining the change in extraction technique will be attached to reports of SCN soil sample results sent out by the ISU Plant Disease Clinic.