One thing most people don’t understand is that it only takes 24 – 48 hours for mold/mildew to start growing!!
Now if you want to use essential oils to help with mold/mildew you can use any of the [anti-]fungal oils.
These are Tea Tree, dill, Geranium , Lemongrass, Rosemary, Thyme (linalool), Cedarwood (atlas), Cajeput, Eucalyptus globulus, Marjoram and Myrrh.
via Birch Hill Happenings Aromatherapy Newsletter Vol 97 Information on the use of essential oils getting started in Aromatherapy, how to use essential oils, What is an essential oil, scenting the artificial tree and more aromatherapy recipes.