Apple scab

Apple Scab is a common disease of apple and other fruit trees caused by the ascomycete fungus Venturia inaequalis. It is one of the most serious and economically damaging diseases affecting apple production worldwide.

Overview

Apple scab primarily affects members of the Rosaceae family, including apple trees, but can also affect other fruit trees like pears and quince. The disease is characterized by dark, scaly lesions on the leaves, fruit, and in severe cases, the twigs and branches of the tree.

Symptoms

The first visible symptoms of apple scab are pale yellow or olive-green spots on the upper surface of leaves. As the disease progresses, these spots darken to a brown or black color and may take on a velvety texture. On the fruit, the lesions are similar in appearance but may cause the skin to crack, affecting the quality of the fruit.

Life Cycle

The life cycle of Venturia inaequalis is closely tied to its host. The fungus overwinters in infected leaves on the ground, producing spores in the spring which are spread by wind and rain to infect new leaves and fruit.

Management

Management of apple scab involves a combination of cultural practices and chemical control. Cultural practices include sanitation measures to remove infected leaves from the orchard floor and pruning to improve air circulation. Chemical control typically involves the application of fungicides during periods of high disease pressure.

Impact

Apple scab is a significant problem for apple growers worldwide, causing substantial losses in yield and quality. The disease also increases production costs due to the need for frequent fungicide applications.

See Also

• List of apple diseases
• Plant pathology
• Fungicide