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 cepa L.) is the second most widely used vegetable crop next to garlic belonging to newlinethe family Amaryllidaceae. Onion crop is affected by several fungal, bacterial and viral diseases, newlinepurple blotch disease caused by Alternaria porri and post-harvest black mold disease caused by newlineAspergillus niger are two major diseases of onion crop. Damages caused by pathogens can produce newline30-45% yield loss. The research was carried out for the management of pre and post-harvest newlinediseases of onion crop by using essential oils of selected botanicals and green manure. In vitro newlineexperiment was carried out in the laboratory of Plant Pathology. Fifty botanical extracts were newlinescreened against Alternaria porri. Ten effective botanicals, vi.z, Allium sativum, Azadirachta newlineindica, Mentha arvensis, Cinnamomum verum, Ocimum sanctum, Nigella sativa, Syzygium newlinearomaticum, Eucalyptus globules, Zingiber officinale and Trachyspermum ammi were selected for newlinefurther evaluation at 25% and 50% concentrations and T11 Mancozeb at 0.1/g (treated check) most newlineeffective 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 newlinethe pathogens Alternaria porri and Aspergillus niger revealed that essential oil treatments T2 newlineAzadirachta indica was found most effective followed by T4 Cinnamomum verum, T5 Ocimum newlinesanctum over untreated control. In-vivo experiment wasconducted at CRF of SHUATS, during Rabi newline2017-2019. The treatment sprayed of essential oil at 0.5%/lit, Azadirachta indica was found most newlineeffective in the reduction of disease severity purple blotch followed by Cinnamomum verum, newlineOcimum sanctum as compared to untreated check and mancozeb at 2g/lit with green manure as newlinetreated check. Among the essential oil treatments maximum plant height, bulb weight, bulb newlinediameter was recorded with T2 Azadirachta indica followed by other treatments. For post- harvest newlineshelf life of onion bulbs, it was observed that T2 (neem) was le