Apple russetting influenced by more than copper sprays
California Agriculture 51(1):11-14. DOI: 10.3733/ca.v051n01p11.
Apple trees are commonly treated with antibiotics during bloom and early shoot growth to control fire-blight, but antibiotic resistance is a concern. To prevent antibiotic resistance, copper treatments may be beneficial, but would be feasible only if stages in bloom or fruit development could be identified that are not subject to fruit russetting. Most fruit russetting results from injury to epidermal cells early in fruit development. Studies in Kern and San Joaquin counties showed copper-induced russetting of apple fruit was unpredictable and sporadic regardless of application timing. Severity of damage varied from year to year.
B.L. Teviotdale is Extension Plant Pathologist, Department of Plant Pathology, UC Davis, located at the Kearney Agricultural Center in Parlier; M. Viveros is UC Cooperative Extension Farm Advisors in Kern and San Joaquin counties, respectively. J.A. Grant is UC Cooperative Extension Farm Advisors in Kern and San Joaquin counties, respectively.
The authors thank Green Valley Farms, Jim Carlisle, General Manager, and John Wood, Assistant Manager, for the use of their orchard in Kern County; Buck and Mark Lewis for use of their San Joaquin County orchard; and UC Staff Associates Dennis Harper, Nancy Goodell, John Fritz, Peggy Schrader and Valeshia Hines for technical assistance, and Carol Adams for statistical advice.