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Abstract The apple scab caused by the fungus Venturia inaequalis (Cke) Aderhold, is one of the most destructive diseases in North Sinai. The fungus is a facultative saprophyte. It grow under cuticular layer of leaves and fruits. It is biotrophic fungus form stroma of short, thick walled cells between the cuticle and the epidermis. These stroma pierce the cuticle to form conidiophores carrying conidia with one septum and slightly curved. At end of winter the mycelium of fungus in overwintered infected leaves on ground form sexual structure known as pseudothecia in the leaves tissue. By the beginning of spring, maturation of pseudothecia was completed and the ascospores released to infect the new leaves. Overwintered apple leaves infected with apple scab play important role for transfers the infection for the following seasons. The fungus is slow growing fungus and require suitable environmental conditions for their growth, germination and infection. Germination and penetration are depending on cultivar susceptibility The amount of total phenolic compounds are varied from susceptible and resistant cultivars. Rubigan, Benomyl, removing attached and overwintered infected apple leaves and Trichoderma harzianum (biological factor) are considered as treatments for control apple scab disease which affect on growth and disease incidence of fungus. |