Nutritional effects of apple trees on Cytospora canker severity (Cytospora cincta) in Semirom orchards

Preliminary studies on nutritional status of 29 commercial Golden Delicious orchards infected to Cytospora canker disease, showed defficiecy of potassium and calcium and excess of nitrogen in most of infected orchard. In this regard, an orchard’s trials was conducted to determine the effects of balanced potassium, nitrogen and calcium elements on prevention of incidence and development of Cytospora canker disease of 27 years apple Golden Delicious cultivar during 2014-15 in the commercial orchard at Semirom, Iran. Eighteen treatments (nitrogen and potassium at 3 levels and calcium at 2 levels) were designed in a factorial complete randomized block design with three replications. The results showed that deviation from optimum percentage index of nitrogen, potassium and calcium is proper option for predicting the occurrence and development of Cytospora canker disease of apple trees. Deficiency or excess of any nutrient caused imbalances in other elements and influenced the severity of the disease extensivily. The highest percentage area under disease progress curve occurred in most of the treatments, that nitrogen rate was less or more than the optimal amount. Combined application of nitrogen and potassium in most of the treatments significantly reduced the predisposing effects of high nitrogen application. The impact of calcium on reducing disease was lower than nitrogen and potassium. This results of this study showed that, balance utility of nutrients such as nitrogen, potassium in soils of Semirom area orchards and spraying of calcium based on recommended manual reduced Cytospora canker disease at 83.79 percent.