The causes of replant disease in organic orchards appear to be different from those in conventional orchards, according to Dr. Mark Mazzola, researcher with the U.S. Department of Agriculture in Wenatchee, Washington. Typically, the major causes of replant disease in Washington are the fungi Cylindrocarpon, Pythium, Phytophthora, and Rhizoctonia, Mazzola has found. Research has shown that organic orchards have less root disease attributed to Pythium than do conventional orchards, but organic orchards have a higher incidence of Rhizoctonia. Pythium and Rhizoctonia are competing fungi—a fact that needs to be taken into account when treatments for replant disease are developed for […]