Apple scab or black spot is caused by the fungus Venturia inaequalis (Cooke) Wint. This disease can infect the aerial parts of apple trees including leaves, petioles, flowers, fruits, pedicels, young shoots and bud scales. It is favoured by cool, rainy and humid spring and summer conditions. If left uncontrolled it can cause significant crop losses.
Leaves and fruits are highly susceptible to apple scab in their early stages of development.