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POSTERS: Cultural control

Multi-site field assessment of bio-renovation methods to control apple replant disease
Shashika Hewavitharana - California Polytechnic University San Luis Obispo. Sara Tianna DuPont- Washington State University, Mark Mazzola- USDA Agricultural Research Service

Commercial scale orchard trials were conducted in the north, central and south districts of the primary apple production region in Washington State to evaluate bio-renovation approaches for the management of replant disease. Treatments examined included anaerobic soil disinfestation using Triticale or Timothy hay (ASD; 8 tons/A), Brassicaceae seed meal (BSM; 1.6 lbs per tree-row-foot rate, 1:1 formulation of Brassica juncea and Sinapis alba) amendment, grower standard soil fumigation (1,3-dichloropropene/chloropicrin), and no-treatment control in randomized complete block design. Soil microbial profiling was conducted at three weeks post-treatment. Anaerobic soil conditions were effectively attained in response to ASD at the north and central sites, but not the south site trial. Significant changes in soil microbial profiles were observed in response to ASD and BSM treatments. In bioassays conducted in orchard soils collected post-treatment, BSM effectively suppressed seedling root populations of Pratylenchus penetrans at all field sites. In addition, BSM, but not fumigation, suppressed lesion nematode root densities recovered from ‘Cosmic Crisp’/G.41 at the end of the first growing season at the central site. Treatment effects on fungal/oomycete root infection detected in seedling bioassays were variable, with Rhizoctonia root infection reduced by ASD and BSM at the central and south sites, respectively.