Tea Tree Oil This is the best working natural mold and mildew remover spray. It can be used on anything that needs mold and mildew removal. Note that the smell of tea tree oil is very strong but will disappear in a day or so, and is non-toxic. Combine 2 teaspoons of tea tree oil with 2 cups of water. Mix in a spray bottle, shake and spray onto any problem areas. Do not rinse to eradicate mold.