There are quite a few factors that influence the appearance of marks on fruits.
According to the expert of the online publication Belnovosti, scientist-agronomist, landscape designer Anastasia Kovrizhnykh , these include insects, diseases and physiological disorders, but first things first.
Bitter Spots
Small depressions, most often found near the calyx, are dark in color. They are dry, spongy, and bitter in taste. They appear due to calcium imbalance.
Cork stains
They look like small discolored depressions and can appear anywhere on the apple flesh. Over time, they expand and penetrate the flesh. Like the previous variant, they are associated with calcium imbalance.
Vesicular spots
They look like brown blisters 4-5 mm in size, with a purple-black halo. They are most often found near the calyx of those fruits that grow outward from the tree, facing the sun.
Black rot
These lesions initially appear as hollow black spots. They are mostly found on fruit close to mummified apples, which in turn are the result of the use of chemical thinners. The lesions later develop into a hard beige or brown rot that has concentric rings and black fruiting bodies or pycnidia.
Soot stains
Soot stains are diffuse marks that range in color from brown to green and have irregular edges. They are more pronounced on light-skinned apples. They are removed by vigorous rubbing.
