ABSTRACT
Apple scab is the most destructive disease of apple throughout the world. Apple scab is an economically important disease resulting in a direct loss from fruit or pedicel infections. Indirectly, repeated defoliation reduces tree growth and yield. The scab pathogen has two stages in its life cycle, the saprophytic stage, which is found on dead leaves, and where the pathogen overwinters. The parasitic stage is the second stage in which the pathogen completes its parasitic life cycle on living parts of the plants, such as on leaves, flowers, twigs, and fruits. The disease causes severe losses to apple nurseries and orchard trees throughout the apple-growing regions of the world. A persistent disease, the severity of powdery mildew and resulting economic loss varies with environmental conditions, cultivar susceptibility, and management practices. Disease is highly destructive both in nurseries and orchards, and the affected plants are killed within a short period depending upon the age of host and environmental condition.
