Assessment of broad spectrum control potential of Eucalyptus citriodora oil against post harvest spoilage of Malus pumilo L.

Abstract

In vitro Eucalyptus citriodora Hook. oil showed potent bioactivity against dominant post harvest fungal pathogens. The minimum bioactive concentrations with fungicidal action of the oil was found to be 1.0 µl ml-1 for Alternaria alternata, Botrytis cinerea, Cladosporium cladosporioides, Colletotrichum capsici, Cyrtomium falcatum, Fusarium cerealis,Fusarium culmorum, Gloeosporium fructigenum, Penicillium digitatum, Penicillium expansum, Penicillium italicum, Penicillium implicatum, Penicillium minio-luteum, 1.2 µl ml-1 for Aspergillus flavus, Aspergillus fumigatus, Aspergillus niger, Aspergillus parasiticus, Curvularia lunata, Fusarium oxysporum, Fusarium udum, Penicillium variable, Helminthosporium oryzae, Helminthosporium maydis, Phoma violacea, and 1.4 µl ml-1 for Rhizopus nigricans. The oil exhibited potency against heavy doses (30 mycelial disc, each of 5 mm in diameter) of inoculum at 2.0 µl ml-1 concentrations. The bioactivity of the oil was thermostable up to 100°C and lasted up to 72 months. The oil preparation did not exhibit any phytotoxic effect on the fruit skin (epicarp) of Malus pumilo up to 50 µl ml-1 concentrations. In vivo trials of the oil as a fungicidal spray on M. pumilo for checking the rotting of fruits, it showed that 30 µl ml-1 concentration controls 100% infection by pre-inoculation treatment, while in post-inoculation treatment, 40 µl ml-1 concentration of fungicidal spray were required for the 100% control of rotting. The fungicidal spray was found to be cost effective (INR 15/L) has long shelf life (72 months) and devoid of any adverse effects. Therefore, it can be used as a potential source of sustainable eco- friendly broad-spectrum herbal pesticide after successful completion of wide range trials. Key words: Eucalyptus citriodora Hook., fungicidal spray, fruit rot, herbal pesticide,Malus pumilo.