Apple – Brown Corky Skin, Russetting
Q: This brown ring is on most of my apples on this years crop. What is it and can it be treated?
A: It looks like apple russet, the brown scarring that sometimes appears on the skin of apples and pears. It is a symptom rather than a disease, which means it can have several different causes: extended periods of high humidity, cool temperatures during early apple development, the application of copper-based pesticides, and powdery mildew infections.
It doesn’t seem to hurt the fruit; usually the taste is unaffected.