Final answer:
The yellow splotches on the leaves of an apple tree are a symptom of a viral infection.
Step-by-step explanation:
The yellow splotches on the leaves of an apple tree are a symptom of a viral infection. Viruses can cause various symptoms in plants, including hyperplasia (abnormal cell proliferation), hypoplasia (reduced cell growth), cell necrosis (cell death), and ring spots (circular or linear areas of discoloration in leaves).
This is supported by the information that symptoms of viral diseases in plants include thin, yellow areas in leaves. Additionally, the reference material mentions ring spots as a symptom of plant viruses.
Distinguishing viral infections from other causes, such as bacterial or fungal infections, can be important for appropriate management strategies.