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Oral: Biological and Cultural Disease Management


Grass residues as a sustainable carbon source in application of anaerobic soil disinfestation for control of apple nursery replant disease
S. Hewavitharana (1), M. Mazzola (2) (1) Washington State University, U.S.A.; (2) USDA-ARS, U.S.A.

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Studies were conducted to assess the efficacy of anaerobic soil disinfestation (ASD) for control of replant disease in an apple nursery setting. Treatments applied in a field trial conducted at an experimental orchard in Washington State included ASD using orchard grass residues (GR; 20 t ha-1) as the carbon source, Telone C35 (27 gal acre-1) and no treatment control (NTC). The apple rootstocks G.935, G.41, and M.9, with respectively decreasing level of tolerance to replant disease, were planted into each of six blocks per treatment with five replicates per rootstock. Post-treatment weed biomass analysis, rootstock growth analysis and rhizosphere fungal community analysis were conducted. Prior to tillage that preceded rootstock planting, ASD yielded significant weed suppression but weed biomass in fumigated plots was comparable to NTC. During the first growing season trunk diameter of G.41 and G.935 rootstocks were significantly increased by ASD compared to the NTC and it was comparable to fumigation treatment. ASD enhanced growth of M.9 relative to NTC but was lower than that for the fumigation. According to TRFLP analysis, different soil treatments possessed unique rhizosphere fungal communities. Based on this study, an increase of 5-25 % gross revenue was projected using ASD based on market value of different rootstocks and sizes. ASD with grass is a potential viable soil-borne disease management practice for the apple nursery industry.