What are these spots on apples?

A number of insects, diseases, and physiological disorders can cause fruit spots, many of which don't appear until harvest. This article lists some of the most common causes observed in apple orchards.

Bitter spots

This is a physiological disorder that often affects apples. Small depressions form on the fruit, especially near the calyx. The tissue in these depressed areas is dark, dry, spongy, and bitter-tasting. The appearance of bitter spots is directly related to a calcium imbalance. Bitter spots on apples appear as small depressions, especially near the calyx.

Cork stains

This type of spot typically appears as small, discolored indentations that can appear anywhere on the fruit's flesh. These spots eventually expand, forming corky patches that penetrate the apple's flesh. Like bitter spots, corky spots are associated with a calcium imbalance in the growing fruit. Corky spots on apples appear as discolored indentations that can appear anywhere on the fruit's flesh.

Vesicular spots

Symptoms appear as small brown blisters (4-5 mm) with a purple-black halo, associated with lenticels on the fruit surface. The first spots are often observed near the calyx of fruits growing outward from the tree, facing the sun. Although lesions rarely penetrate the flesh more than 1-2 mm deep and do not cause fruit rot, multiple spots may appear on a single fruit, significantly reducing its marketability in the fresh market. Damage is caused by brown blisters (4-5 mm) with a purple-black halo, associated with lenticels on the fruit surface.

Black rot

Black rot lesions initially appear as hollow black spots, often near mummified fruit caused by the use of chemical thinners. These lesions eventually spread to form a hard beige or brown rot with concentric rings and black fruiting bodies or pycnidia.

Bitter rot

Bitter rot appears as brown spots that spread into sunken lesions, often surrounded by a red halo. Particularly in wet weather, salmon-colored spore masses form on the surface of the lesions. A typical V-shaped rot develops toward the heart when the infected fruit is cut. Bitter rot appears as brown spots that enlarge into sunken lesions, often surrounded by a red halo.

Soot stains

Diffuse brown to green spots with irregular edges appear on the apple skin, often more noticeable on light-skinned fruits. These spots can be removed by vigorous rubbing. During storage, fruits infected with soot stains bruise more quickly than healthy ones. Soot stains initially range in color from brown to olive green, appear indistinct, and have irregular edges on the skin surface, often more pronounced on light-skinned fruits.