Alternatives to Fumigation for Control of Apple Replant Disease in Washington State Orchards

Introduction The poor growth of fruit trees that occurs after replanting on a site that previously supported the same or closely related species is termed “replant disease.” In apple, replant disease is widespread and has been documented in all of the major fruitgrowing regions of the world (Traquair, 1984). Apple replant disease is characterized by uneven growth of young trees but, when severe disease pressure is encountered, poor growth may be exhibited by a majority of trees on the site and death of young trees may occur. Symptoms of apple replant disease include severe stunting, shortened internodes, rosetted leaves, small root systems, decayed or discolored roots, and reduced productivity. Affected trees have less lateral roots and few root hairs.