Chemical treatments in Golden Delicious Spur fruits in relation to russeting and nutritional status

The impact of chemical products on mineral nutritional status and russeting in 'Golden Delicious Spur' was studied. In addition, we sought to define the nutrients responsible for russeting in order to avoid imbalances in their concentrations in the fruit. Lime-sulphur (lime and sulphur, T1), ProVide (gibberellic acid GA(4+7), T2), calcium nitrate (8.5% N and 11.5% Ca, T3), Microthiol Special (micronized wettable sulphur at 80%, T4), Packhard (8% Ca, 6% carboxylic acid, 0.5%B, T5), and Dithane (ethylene-bis dithiocarbamate of manganese 62%, Mn 16% and Zn 2%, T6) were applied to apple trees at the onset of flowering, at petal drop, and at the onset of fruit development. The ProVide and Microthiol treatments reduced the damaged fruit area and the percentage of damaged fruits in comparison to control (trees without application, T0). The application of calcium nitrate and Dithane increased the percentage of damaged area in relation to control, whereas the use of Packhard increased the percentage of fruits with russeting. In conclusion, our results indicate that russeting is more influenced by the formulation of the chemical products than by the nutrient content in the fruits, although we found a highly significant reduction and inversely proportional relationship between the Mn concentrations and the appearance of russeting.