The growth of apple seedlings (Malus domestica Brokh.) is negatively correlated with soil arsenic and zero growth occurs at about 450 ppm total arsenic. Soil arsenic concentrations less than 150 ppm, which are frequently found in orchard soils, contribute less to the replant problem than biological factors. Growth of apple trees was increased 50% or more by preplant soil fumigation with methyl bromide or trichloronitromethane (chloropicrin) in 87.5% of the trials in 17 apple orchard soils tested. Non-specific plant pathogens in orchard soils attack cereals as well as apple seedlings, but apple orchard soils also contain an entity that specifically affects apples. This is probably the same unknown entity that is responsible for specific apple replant disease in Europe, Australia, and elsewhere.
Received for publication August 22, 1977. Scientific paper no. 4879, College of Agriculture Research Center, Washington State University, Pullman, WA. Project No. 0210.
Horticulturist and Soil Scientist, and Associate Plant Pathologist, respectively. Tree Fruit Research Center, Wenatchee, WA 98801.
Plant Pathologist, Northwestern Research and Extension Unit, Mt. Vernon, WA 98273.