Lesion nematodes (Pratylenchus sp.) are recognized as pathogens of apples in the eastern part of the United States, and various preplant control measures have been demonstrated beneficial in re-establishing orchards. During the early '60s two small-scale preplant fumigation trials were conducted in replanted orchards in the Oak Glen area of San Bernardino County, California. Many tree replants or interplants in established orchards in this area were dying or demonstrating lack of vigor at that time. Soil and root analysis showed that high populations of Pratylenchus sp. were present in the orchards and were believed to be a major contributing factor to tree failure in these orchards. The results of these two early trials showed that preplant measures for nematode control were beneficial.