Etiology of spot occurrence on apple fruits in Semirom region, Iran

In recent years, spot symptoms occurred and developed on fruits of apples in the commercial orchards of Semirom, Iran. Plant protection investigations revealed different causes inducing the spots on fruits. The possible causes were Apple Chlorotic Leaf Spot Virus, Apple scar skin viroid, Fusicladium pomi, Altenaria mali, apple green aphid, pentatomid bugs and nutritional disorders. Regarding symptoms of calcium disorders on trees, random samplings were conducted on trees of Red Delicious and Golden Delicious. Then concentration of minerals (calcium, potassium, magnesium and nitrogen) were determined in a compound sample for each garden and the ratios of N/Ca2, Kﰦ, Mg2ﰦ, (K)/Ca2 and (N⯯貃)/Ca2 were calculated. Orthogonal contrasts between treatments with and without symptoms, showed significant differences for ratios of Kﰦ, (K)/Ca2 and (N⯯貃)/Ca2. Therefore, the disorder has negative relation with potassium content and Kﰦ ratio and positive relation with calcium content in the fruit. Symptoms inspection showed that there types of calcium disorders were found in apple commercial orchards of Semirom, including bitter pit (on both varieties), corky spot (on Red Delicious) and lenticel blotch pit (on Golden Delicious).