Plant-parasitic nematodes are microscopic worms, usually soil borne, that feed on plants. Nematodes that feed on and damage corn have been known to occur in Iowa and other parts of the Midwest since the 1950s. But recent and upcoming changes in Iowa's cropping practices have some anticipating an increase in damage and yield loss to corn from nematodes. Most corn nematode species maintain their populations when soybeans or alfalfa are grown, but repeated cropping of corn may cause nematode populations to flare up. Also, use of transgenic, insect-resistant corn hybrids for corn rootworm control may reduce the amount of soil-applied insecticide used in the state, and some have speculated that these insecticides may have provided some suppression of plant-parasitic nematode populations in the past. So reduction in use of soil insecticides may lead to increases in corn nematode population densities. In addition to the many nematode species that have been known to parasitize corn for decades, a new species of cyst nematode feeding on and damaging corn was discovered in 2006 in Tennessee. This nematode could possibly pose a new threat to corn production. The potential for corn yield loss caused by nematode feeding has largely been ignored in the past 20 years. The recent, increased concern about corn nematodes represents both a renewed interest in some old foes and concern about a possible new nemesis.