Pour 2 cups of warm water into a clean spray bottle. Add 2 teaspoons of tea tree oil.
Secure the lid on the bottle tightly. Shake up the bottle to mix the tea tree oil and water.
Spray the tea tree mixture onto the mildew spots on the rug. Make sure the spots are completely covered with the mixture, but not soaking wet.
Scrub the spots lightly with a clean scrub brush to remove the mildew. Let the tea tree oil dry onto the rug without rinsing. Repeat as necessary until the mildew is gone.
Pour 1 cup of white vinegar into a clean spray bottle. Add 25 drops of tea tree oil.
Secure the lid on the bottle tightly. Shake the bottle to mix the ingredients.
Spray the tea tree and vinegar mixture onto the rug. Leave it there for 10 minutes.
Scrub the rug gently with a sponge dampened with water until the mildew disappears. Repeat if necessary to remove all the mildew.