Studies on post-harvest orange rot control with essential oils

Twelve essential oils, extracted by hydrodistillation, were tested at different concentrations against four fungi known to cause post-harvest rot of orange fruit, i.e. Botrytis cinerea, Penicillium expansum, Phytophthtora citrophthora and Mucor spp. Plant species used as a source of these volatile fractions were Carum carvi, Foeniculum vulgare, Pimpinella anisum (Apiaceae), Hyssopus officinalis, Lavandula angustifolia, Majorana hortensis, Melissa officinalis, Ocimum basilicum, Origanum vulgare, Salvia officinalis, Thymus vulgaris (Lamiaceae), and Verbena officinalis (Verbenaceae). Preliminary experiments carried out in vitro showed that only essential oils from V. officinalis, T. vulgaris and O. vulgare showed some fungistatic action against the above fungi. Thus, only these three essential oils were used in successive in vivo tests to protect healthy orange fruits of cv. Washington from artificial infection by the same micromycetes. Essential oil from T. vulgare at 2000 ppm controlled fruit rot by B. cinerea, P. citrophthora and Mucor spp. but was ineffective against P. expansum. Essential oils from V. officinalis and O. vulgare inhibited infection by the former couple of fungi and by P. citrophthora only, respectively.