Wear rubber gloves to protect your skin from dryness or irritation caused by your cleansing solution.
Mix 1 cup bleach with 1 gallon warm water in a bucket. Dip a scrub brush in the bleach solution and scrub the mildew stained areas on your garden statute. Apply more bleach solution to your brush and continue to scrub the entire surface affected by mildew.
Rinse your garden statue off with a garden hose. Start rinsing at the top of the statue and work your way down to make sure the mildew spores are rinsed off.
Air dry your statue completely. If it's small enough to be moved, place the statue in direct sunlight to dry. Sunlight naturally kills mildew and will get rid of any remaining mildew spores and stains.