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Effect of Production System and Pruning on Temporal Development of Cercospora depazeoides and on Berry Yield in Black Elderberry Orchards

In a 2-year study, the temporal development of Cercospora leaf spot (Cercospora depazeoides) and berry yield were evaluated in two production systems (integrated and organic) and in two winter pruning treatments (trees pruned to four and eight scaffolds) in two black elderberry (Sambucus nigra) orchards in Hungary. Under organic production, leaf spot onset occurred 2 to 4 weeks earlier (mid- and late July) in both years and both orchards compared with the integrated program. Disease then continuously progressed until the final assessment date (late September) in both years, reaching a maximum final disease incidence of 15.9% in the integrated system and of 38.2% in the organic system. In general, disease progress after late August was greater on trees pruned to eight scaffolds than on trees pruned to four scaffolds in both production systems. Both final disease incidence and area under the disease progress curves (AUDPC) were significantly lower (P < 0.001) in the integrated treatments compared with organic ones. Across all treatments, both disease measures were significantly (P < 0.05) lower on trees pruned to four scaffolds compared with trees pruned to eight scaffolds. However, when the effect of pruning on final disease incidence and AUDPC was analyzed separately for integrated and organic systems, pruning caused uniformly significant differences in disease development only for the organic system. Berry yield was significantly higher (P < 0.05) in the integrated system compared with the organic system, but pruning showed no significant effect on yield. Overall, pruning to four scaffolds resulted in consistently lower disease development in organic production compared to integrated. Thus, winter pruning may be useful as a Cercospora leaf spot management practice in organic elderberry orchards.