Criconemoides species Ring Nematode Damage to Turf.   Ring nematode damage to turf usually occurs only at high populations. Most common on golf course greens. Biology.   The ring nematode is an ectoparasitic nematode and feeds on interior portions of the roots but is found in the soil outside of the root. Criconematinae are markedly annulate stubby nematodes, ranging from 0.2 - 1.0 mm in length.  Ecology.  Large populations  usually occur only in highly sandy soil. Symptoms. Yellowing, moisture-stress wilting and poor growth in above-ground foliage. Damage to other crops.   Peanuts are also a host of ring nematode.