Clip leaves that contain red or brown mold spots. Fungus makes small spots on the leaves where spores breed.
Water the ivy with a drip hose as opposed to sprinkler or watering can. Water hits the leaves and spreads the spores. Drip hoses lay around the ivy and slowly drip water directly into the ground.
Cover the ground around and under the ivy with mulch. Mulch helps eliminate the back splash caused by pouring water and rain.
Apply a fungicide as needed if you can't control it naturally. Lawn and garden stores sell a variety of fungicide. All natural fungicide is available.