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Apple Disease Control and Bloom-Thinning Effects by Lime Sulfur, Regalia, and JMS Stylet-Oil

C. N. DeLong, K. S. Yoder, A. E. Cochran II, S. W. Kilmer, W. S. Royston, Jr., L. D. Combs, and G. M. Peck

May 2018

Research

Apple (Malus × domestica Borkh.) growers require management practices that will produce high-quality fruit while minimizing the number of chemicals used for adequate disease control and horticultural practices. Certain chemicals applied for bloom thinning also have fungicidal properties and could provide protection against early season diseases in addition to crop reduction. Over 5 years, treatments of lime sulfur (LS), Regalia (an organically approved biofungicide), and JMS Stylet-Oil (JSO) were evaluated for protection against apple scab (Venturia inaequalis [Cooke.] G. Wint.), powdery mildew (Podosphaera leucotricha [Ellis & Everh.] E. S. Salmon), cedar apple rust (Gymnosporangium juniperi-virginianae Schwein.), and quince rust (Gymnosporangium clavipes [Cooke & Peck] Cooke & Peck in Peck), as well as crop load reduction and fruit finish. Both LS and Regalia reduced apple scab and cedar apple rust in four out of five test years. Treatments of Regalia applied with JSO provided disease protection and crop load reduction similar to LS applied with JSO. We provide evidence that LS and Regalia, applied as bloom thinners, can reduce chemical applications used during bloom by combining two chemical spray functions: one for disease protection and one for crop load management.

doi:10.1094/PHP-10-17-0065-RS

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