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Effect of Sanitation Treatments on Leaf Litter Density and Leaf Spot Incidence in Integrated and Organic Sour Cherry Orchards

A 3-year study was conducted to determine the effect of five sanitation treatments on leaf litter density (LLD), leaf spot incidence, and percent defoliation on two cultivars (‘Újfehértói fürtös’ and ‘Érdi bőtermő’) in two sour cherry orchards: one managed by integrated pest management principles with conventional fungicides and the other managed organically. The following sanitation treatments were compared: sprays of urea or lime sulfur in autumn, removing fallen leaves after leaf fall, straw mulch cover in late winter, sprays of urea or lime sulfur followed by mulch cover, removing fallen leaves followed by mulch cover, and a nonsanitized control. In both orchards and all years, LLD decreased by 2 to 28% in all treatment plots from early December to mid-May. LLD reduction was two to four times higher in the organic orchard compared with the integrated orchard. All treatments, except the lime sulfur or urea treatment alone, resulted in significant (P < 0.05) reduction of LLD in both the integrated and organic orchards compared with nonsanitized plots. Only leaf removal alone or in combination with mulch significantly (P < 0.05) reduced cherry leaf spot incidence and percent defoliation (by 11 to 70% and 15 to 72%, respectively) compared with nonsanitized plots. The application of these sanitation treatments in orchard management practices is discussed.