Temporal Dynamics of Incidence of Shot Hole Disease Affected by Training Systems and Cultivar Susceptibilities in an Integrated Plum Orchard

Shot hole disease (SHD) can cause severe epidemics in plum orchards, depending on cultivar susceptibility and training system; however, the combined effect on the progress of temporal disease and on the possible reduction in SHD in the disease management was not investigated. The aim of this 3-year study was (i) to monitor and analyze the temporal dynamics of SHD progress under four training systems (4 x 1.5, 4 x 2, 5 x 2.5 and 6 x 3 m) and on four plum cultivars ('Cacanska lepotica', 'Bluefre', 'Stanley' and 'President') in an integrated plum orchard; (ii) to identify those time periods when training system and cultivar combinations can reduce the disease development. Both SHD incidences and the area under the disease progress curves (AUDPC) were significantly affected by the training system, cultivar and year. Plum cultivars with high or mid-high susceptibility to SHD showed continuous SHD development from May to November, while cultivars with low susceptibility to SHD showed no symptoms until mid-summer and then progressed slowly until November. High (4 x 1.5 m) vs. low (6 x 3 m) density training systems reduced SHD incidence and AUDPC consistently for three cultivars ('Cacanska lepotica', 'Stanley' and 'President') in September, October and November, compared to the high-density training system. Only cv. 'Bluefre' showed no effect either on disease incidence or AUDPC, due to very high disease incidences in all training systems from September to November. In conclusions, combinations of training system and cultivar can significantly reduce SHD incidence, which may be successfully used as a part of the integrated pest management approach during the establishment new plantations.

Automated summary

Different combinations of training systems and cultivars can affect the development of SHD and reduce disease progress at specific time periods. Cultivars with high susceptibility to SHD showed continuous disease development from May to November, while cultivars with low susceptibility showed no symptoms until mid-summer. High-density training systems (4 x 1.5 m) consistently reduced SHD incidence and disease progress for three cultivars.