Effect of sanitation treatment and cultivar on saprophytic development of Blumeriella jaapii in integrated and organic sour cherry orchards

Abstract

A three-year study was conducted to determine the effect of urea and lime sulphur sanitation treatments on three saprophytic development stages of Blumeriella jaapii on two sour cherry cultivars in integrated and organic orchards. The sanitation treatments in the integrated orchard included sprays of urea applied in the autumn, sprays of urea followed by mulch cover, and non-sanitized control. Urea was replaced with lime sulphur in the treatments in the organic orchard. The percent survival of three saprophytic development stages of B. jaapii (i.e., saprophytic hyphal growth, mycelial aggregates, and presence of apothecia and/or winter acervuli) ranged between 11 and 70 % and between 21 and 67 % in the urea and lime sulphur treatments, in the integrated and organic orchards, respectively. In all years, all urea and lime sulphur treatments significantly (P < 0.05) reduced the percent survival of the three development stages of B. jaapii compared to non-sanitized plots in both orchards and on both cultivars. Treatments that included a mulch cover resulted in a generally lower percent survival of the three development stages of B. jaapii than treatments that did not include the mulch cover, but their significance varied among the B. jaapii development stages, for years, cultivars and orchards. An interpretation of the importance of these sanitation treatments for orchard management practices is discussed.