Water retention on the surface of apples and sweet cherry leaves and fruits

Surface water retention of leaves and fruits of apple ( Malus domestica Borkh.) and sweet cherry ( Prunus avium L.), was evaluated under controlled environmental conditions in order to determine the retention potential at different growth stages. Dipping and spraying, with and without non-ionic surfactant, were used as application systems. Water retention was expressed as the ratio between the weight difference of the organ before and post application and organ weight before application. Leaf water retention by dipping was 62 and 64% for ‘Royal Gala’ and ‘Fuji’ apples, respectively, and 37 and 50% by spraying. The surfactant tended to reduce foliar water retention by spraying on both species. An exponential reduction of fruit water retention was observed during their growth. Fruit dipping generated the highest water retention, with values of 50% at the earliest stage. Then, water retention stabilized at 1–2%, when the apples and sweet cherries diameter reached 25 and 15 mm, respectively, despite dipping or spraying. The surfactant tended to increase water retention at early fruit stages and to reduce it with fruit growth. These results can be useful for estimating the potential residue on leaves and fruits in apple and sweet cherry trees, in both the orchard (spraying) and the packing house (dipping).