Assessment of yield losses due to purple blotch in onion (Allium cepa L.) and its management

Onion is one of the most important commercial vegetable crop grown in Pakistan. Onions are grown in every part of the world where plants are farmed and can be grown from seeds, bulbs or sets. It is valued for its distinct pungent flavor and is an essential ingredient for the cooking in many regions. Onion is the queen of the kitchen. Onion is preferred mainly because of its green leaves, immature and mature bulbs. A number of diseases attack on onion crop but purple blotch is the most important one and cause huge losses in different parts of world. To search out source of resistance against this disease, twenty one varieties/ lines were evaluated against it. Out of these varieties, not even single variety shows highly resistant/immune response towards disease with rating 0, One variety i.e. Phulkara exhibited resistant response while five varieties/lines i.e. Desi red, Early red, Robina, Dark Red, Mirpurkhas showed moderately resistant response. VRIO-6, VRIO-1, VRIO-4 Red nasik, Desi black expressed moderately susceptible response and five i.e.VRIO-9, Pak-10321, Faisalabad Red, Pusa red, Red imposta expressed susceptible reaction while VRIO-3, VRIO-5, VRIO-8, VRIO-7, VRIO-2 showed maximum disease development with rating 5 towards purple blotch disease. For management three fungicides and three plant extracts at three concentrations were evaluated against purple blotch disease of onion under field conditions. Among these fungicides Mancozeb expressed minimum disease incidence (22.22), followed by Score (36.54), Dorazole (43.31), Dora (54.05), as compared to control as shown in (table 4.3) and (fig 4.2). Mancozeb expressed maximum reduction in disease after 1st (25.95), 2nd (22.47) and 3rd spray (18.24) % followed by Score. (40.17), (36.61), (32.84) %, Dorazole (47.73), (42.94). (39.25)% and Dora (57.76), (54.14), (50.27) % as compared to control. Similarly among plant extracts. Moringa oleifera expressed minimum disease incidence (43.84), followed by A. indica (51.08), A. sativum (60.73) as compared to control as shown in (table 4.8) and Moringa oleifera expressed maximum reduction in disease after 1st (47.80), 2nd (43.88) and 3rd spray (39.85) % followed by A. indica (54.65), (51.35), (47.25) % and A. sativum (64.38), (60.88), (56.93)%, % as compared to control.