Apple scab disease | Full explanation | For competitive exam

GBP SCIENCE @ gbpscience 322

Apple scab disease | Full explanation | For competitive exam

Apple scab disease is fungal disease caused by ascomycetous fungus I.e., Venturia inaequalis.
Primary infection starts from ascospores ( It is sexual spore of apple scab)
Symptom and sign of apple scab

Apple scab infections are initiated in early spring on emerging and young leaves. Early lesions appear 10 days later as lighter green areas compared to the surrounding leaf tissue. Lesions increase in size and become olive-colored and velvety as a result of asexual spore production (conidia) .Scab lesions that form on young leaves may expand to more than 1 cm in diameter. Ontogenetic resistance of older leaves, however, usually results in smaller lesions or no visible symptoms. Affected tissues eventually may become distorted and puckered, and leaf lesions become cracked and torn. Severely infected leaves drop from trees. Two to three consecutive defoliation events can weaken trees, resulting in a greater susceptibility to other stresses such as of freeze damage, insect injury, and other diseases.
Fruit lesions are generally blistered and "scabby" in appearance, with a distinct margin .The earliest noticeable symptom on fruit is water-soaked areas that rapidly develops into velvety, green to olive-brown lesions. Infections of young fruit cause fruit distortion as healthy tissue continues to grow (Figure 5). Severely infected fruit often drop prematurely from trees.


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