1. Early blight of Potato and Tomato

2. Symptoms Foliar symptoms of early blight first appear as small, irregular to circular dark brown spots on the lower (older) leaves. These may range in size from a pinpoint to an eighth of an inch in diameter. As the spots enlarge, they become restricted by leaf veins and take on an angular shape. Angular spot on upper leaves

3. Spots enlarge, and by the time they are one-fourth inch in diameter or larger, concentric rings can be seen in the center of the diseased area. The central tissues and concentric rings are forms a target board or bull’s eye appearance Potato (concentric rings) Tomato (concentric rings)

4. A narrow band of chlorotic tissue often surrounds each lesion (Yellow halo) and extensive chlorosis of infected foliage develops over time. Tomato (Yellow halo) Potato (Leaf chlorosis)

5. By the end of the growing season, the upper leaves of infected potato plants may be peppered with numerous small early blight lesions and subsequently lesions may coalesce to cover a large area of the leaf. Peppery and wilted leaf in potato

6. On the stems are brown to black necrotic lesions develop, sometimes girdling the plant if they occur near the soil line. Tuber symptoms of early blight include circular to irregular lesions that are slightly sunken and often surrounded by a raised purple to dark brown border. The underlying tissues are leathery to corky in texture, dry and usually dark brown Potato tuber infection (in very severe case)

7. Etiology C.O. - Alternaria solani Mycelium – Septate, branched, light brown Conidiophores – Emerge through stomata, short, septate, dark Conidia – Brown, obclavate in shape, produced singly at apical cell of conidiophore Beaked, muriform, transverse, longitudinal and oblique septa

9. Perpetuation and Spread Perpetuation: The conidia and the mycelium in the soil or in the debris of the affected plants can remain viable for more than 17 months. These conidia or the new conidia found on the overwintered mycelium bring about the primary infection of the succeeding potato crop. Spread: The conidia formed from the primary infection are transported by water, wind, insects, other animals including man, and machinery.

10. Epidemiology High humidity Frequent rains Followed by Warm and dry weather Optimum temperature for conidia germination 28 - 30°C

11. Management Certified disease free seed tubers should be planted. Plant debris to be collected and destroyed by burning Crop rotation with non-host crops. Very early spraying with Zineb @ 0.2% and repeating it for every 15 – 20 days gives effective control. Some systemic products that have shown good efficacy against early blight are Propiconazole, Difenoconazole, Azoxystrobin, etc @ 0.1%

12. Late blightEarly blight 1. The symptoms starts from the leaf margin 1. The symptoms starts form the middle of leaf 2. The spots are irregular in shape 2. The spots are roundish and have concentric rings 3. The spot may be sometimes surrounded by green halo. 3. The spot may be surrounded by yellow halo 4. The spot is not restricted by the veins i.e. the spot continues to grow beyond the leaf veins 4. The spot is restricted by the veins and so the spot s take angular shape 5. There is whitish cottony growth on the under surface of the leaves 5. There is no such growth on the under surface of the leaves. Difference in Symptoms between Late Blight and Early Blight of potato and tomato