Radical cracking develops at the fruit center from the radical part of the stem towards the center of the fruit. Fruit suffers from radiation. Concentric rings that are found on the fruit leads to cracking. Fruit cracking is a gradual process, and it takes place in three stages: the initial, middle and later stages of fruit cracking. At the initial stage of fruit cracking, a brown stripe begins to appear on the surface of the fruit and the cuticles fracture. Then, a crack becomes visible, with the oil glands starting to deform. The oil glands suffer severe rupturing after which tissues of the fruit surface and the cells are severely damaged and there is a larger space among cells of the broken albedo.
Disorders can be developed post-harvest due to adverse environmental conditions such as temperature, humidity, and handling practices, while pre-harvest factors responsible for the disorders could be due to the deficiency of micronutrients such as boron, copper, and manganese. The fruit size and shape index also have certain effects on citrus fruit cracking. Larger fruits are more likely to experience the cracking phenomenon. The influence of rootstock on citrus fruit peel creasing and fruit cracking is indirect. Daily variations in the light exposure intensity positively correlate with the daily fruit creasing. The daily fruit creasing rate positively correlates with daily variation values in light intensity. The higher average relative humidity before the physiological fruit dropping period will increase the occurrence of fruit creasing. Insufficient nutrients in the partial peel will cause developmental and metabolic disorders in the peel. Hence, the stimulation from an external adverse environment will result in fruit creasing and cracking.
Reduce heavy losses by extra attention before and during critical periods. Sufficient water and nutrients should be made available to the trees. Add clay and compost to improve the soil condition. Slowly release fertilizers and use compost to feed the trees to stop the sudden spurts of nutrients. Reduce evaporation by retaining soil moisture using mulch.
Always consider an integrated approach with preventive measures together with biological treatments, if available. Spray calcium compounds or GA3 at 120 ppm on young fruits to minimize fruit cracking. Spray treatments of potassium fertilizer, calcium fertilizer, and boron fertilizer to significantly decrease the creasing fruit. Apply potassium during the early fruit development to promote fruit peel development, increase peel thickness, enhance fruit cracking resistance ability and reduce pre-harvest fruit cracking.
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