High populations of both Scutellonema brachyurum and Macroposthonia xenoplax were detected in the root zones of peach trees growing at sites where peach tree short life occurred. Both nematodes responded to changes in tree health, with the highest numbers detected under the most vigorous trees; both populations declined as tree vigor declined. Few of either species were detected 6 months after trees died. The nematode populations were inversely correlated with each other. More M. xenoplax were recovered during cool, wet weather, but moisture seems more important than temperature in influencing population levels. Most S. brachyurum were recovered during hot, dry weather.