Effect of green manure and essential oils of selected botanicals on Alternaria porri and Aspergillus niger causing pre and post harvest diseases of onion

Abstract

Onion (Allium cape L.) is the second most widely used vegetable crop next to garlic belonging to the family Amaryllis decease. Onion crop is affected by several fungal, bacterial and viral diseases, purple blotch disease caused by Alternaria pore and post-harvest black mold disease caused by Aspergillus Niger are two major diseases of onion crop. Damages caused by pathogens can produce 30-45% yield loss. The research was carried out for the management of pre and post-harvest diseases of onion crop by using essential oils of selected botanicals and green manure. In vitro experiment was carried out in the laboratory of Plant Pathology. Fifty botanical extracts were screened against Alternaria pore. Ten effective botanicals, viz, Allium sativum, Azadirachta Indica, Mentha arvensis, inn amomum velum, Osmium sanctum, Nigella sativa, Syzygies aromatic, Eucalyptus globules, Zingier officinal and Trachyspermum ammi were selected for further evaluation at 25% and 50% concentrations and T11 Mancozeb at 0.1/g (treated check) most effective treatment was T2 Azadirachta Indica. Essential oils of 10 botanical extracts at 0.2% and newline0.5% and fungicide Mancozeb at 0.2% for the inhibition of radial mycelial growth (mm) of both the pathogens Alternaria pore and Aspergillus Niger revealed that essential oil treatments T2 Azadirachta Indica was found most effective followed by T4 Cinnamomic verum, T5 Ocimum sanctum over untreated control. In-vivo experiment wasconducted at CRF of SHUATS, during Rabi 2017-2019. The treatment sprayed of essential oil at 0.5%/lit, Azadirachta indica was found most effective in the reduction of disease severity purple blotch followed by inn amomum verum, Ocimum sanctum as compared to untreated check and mancozeb at 2g/lit with green manure as treated check. Among the essential oil treatments maximum plant height, bulb weight, bulb diameter was recorded with T2 Azadirachta indica followed by other treatments. For post- harvest shelf life of onion bulbs, it was observed that T2 (neem) was le