apple scab A very common disease of apple trees (Malus) in which the most obvious symptom is the appearance of superficial, dark, corky scabs on the fruit. In general the disease is not serious in itself, although more serious secondary infections can occur. The causal agent of apple scab is a fungus, Venturia inaequalis.

apple scab A very common disease of apple trees (Malus) in which the most obvious symptom is the appearance of superficial, dark, corky scabs on the fruit. In general the disease is not serious in itself, although more serious secondary infections can occur. The causal agent of apple scab is a fungus, Venturia inaequalis.