Criconemoides species. Ring Nematodes Damage to Corn.   Ring nematodes associated with corn usually occur with mixed populations of other species, and are considered responsible for reduction in yield. Biology.   Criconematinae are markedly annulate stubby nematodes, ranging from 0.2 - 1.0 mm in length.  Ecology.   Large populations around corn usually occur only in highly sandy soil. Symptoms.  Damage to other crops.   Peanuts are also a host of ring nematode. Control.   Rotation with cotton and soybeans has been found to be effective