Macroposthonia xenoplax Ring nematode Damage.  At high population densities, this nematode can cause extensive root pruning which stresses the plant and reduces yields.  Biology.  Macroposthonia spp. gets its common name from the markedly annulate cuticular ring ornamentation around its body.  They are stubby nematodes, ranging from 0.2 - 1.0 mm in length.  Ecology.  Macroposthonia xenoplax has been reported from North and South America, Europe, Africa, India, Australia, and Japan.  Symptoms.   Plant stress and reduced yields. Damage to other crops.  Ring nematode affects peach, almond, apricot, cherry, plum and walnut; also lettuce, carnation, and pine. Control.  Cultural control (using clean root stock), an chemical control are effective.  Links and References.  Grape nematode (Ring).  Oregon State University.