In autumn, many garden owners experience brown spots appearing on the skin of otherwise healthy apples. These symptoms can be alarming, but they do not necessarily indicate an infection. In our article, we have collected the most common causes and also show how to distinguish and treat them. The round, sunken brown spots on the skin of apples are often signs of the so-called bitter pit (bitter spotting). This is not an infectious disease but a physiological disorder caused by a lack of calcium. The diameter of the spots is typically 2-10 mm, and the fruit flesh underneath can be spongy and dry. The symptoms are particularly common in large-fruited varieties, especially if they are harvested too early or if the trees do not receive adequate water and nutrients. The calcium deficiency often results from the calcium in the soil being inaccessible to the plant – for example, due to low pH or excessive potassium-magnesium imbalance. If the brown spots are irregular in shape, spreading, ...