Star crack

Star crack is a physiological disorder affecting apple trees, characterized by the appearance of star-shaped ruptures on the skin of the fruit. Unlike diseases caused by fungi or bacteria, this condition is purely non-infectious, resulting from the inability of the fruit skin to accommodate rapid internal growth during specific environmental or nutritional conditions.

The primary symptoms are distinct, radial cracks that emerge on the surface of the apple, often centered around the calyx or the stem end. As the fruit continues to develop, these cracks can deepen and become corky, resulting in a scarred, unattractive appearance that makes the produce unsuitable for commercial sale.

The development of star crack is highly dependent on environmental fluctuations, particularly erratic water supply. Periods of drought followed by heavy rainfall or excessive irrigation cause the internal cells of the fruit to expand rapidly. If the skin's elasticity is compromised, it cannot stretch quickly enough, leading to structural failures in the form of these cracks.

The economic impact of this disorder is significant, as it leads to high post-harvest losses. Beyond the immediate loss of fruit quality, the damaged skin provides an entry point for secondary infections and pests, which accelerates the decay process significantly during the storage period.

Prevention involves careful management of the orchard environment. Key strategies include maintaining consistent soil moisture through controlled irrigation and utilizing mulching techniques. Furthermore, regular foliar applications of calcium and balanced fertilization programs that avoid nitrogen excess help reinforce the structural integrity of the apple skin, reducing the risk of star crack development.