Source: Greg Tylka, Iowa State University

Fall is NOT a good time to collect soil samples to check for corn nematodes. Corn nematode population densities (numbers) typically decrease in the latter part of the growing season. And it is not possible to calculate back in time to determine what the numbers were in the earlier part of the growing season. Therefore, low corn nematode numbers obtained from fall soil samples are not very informative. Of course, if population densities of corn nematodes are high in soil samples collected in the fall, it is reasonable to assume that the numbers were high earlier in the season as well.

Fall is ideal time to collect soil samples to test for soybean cyst nematodes (SCN), in contrast to the situation with corn nematode soil sampling. Fields in which corn or soybeans were grown in 2009 can be sampled for SCN. Sample results will indicate if fields are infested with SCN or if SCN population densities are being kept in check in SCN-infested fields that have had SCN-resistant varieties grown in the past.

Original press release