Which of the following is not a disease of apple

Answer: Option D

The bunchy top is not a disease of apples, whereas all other given in options affect apples.
Birds eye : The disease appears first as dark red spots on the berry. Later, these spots are circular, sunken, and ashy-gray and in late stages, these spots are surrounded by a dark margin which gives them the "bird's-eye rot" appearance.
Powdery mildew: It is caused by the fungus Podosphaera leucotricha, which forms a dense white fungal growth (mycelium) on the host tissue and affects: the leaves and buds.
Downey mildew: Downy mildew is a disease of foliage, caused by a fungus-like (Oomycete) organism. It is spread from plant to plant by airborne spores.