Does a negative SCN soil test result prove that the field is not infested with the nematode?
Not finding SCN in a soil sample does not prove that it is not present in the field from which the sample was collected for two reasons. First the extraction procedures used to recover cysts and eggs of SCN from soil are not 100 percent effective. Consequently, some samples that contain low levels of SCN may not test positive when the soil is processed for the nematode. Second, the distribution of SCN can be variable in a field (see the answer to question 3), and it is possible that soil might have not been collected from the areas of the field that are infested with the nematode. A field from which a sample with a negative SCN test is obtained most likely does not have a substantial SCN infestation, but follow-up sampling is recommended to check for SCN infestations that become established in future years.
