Organic Garden Bug Spray. ONION SCRAPS- Save your onion skins, peels and ends then refrigerate in an empty tub until full. Place the onion pieces in a pail and fill with warm water. Soak for a few days to a week. After a week, strain it and store it in spray bottles. Bury the onion bits around plants that are prone to aphids, spiders and other pests. Just spray both house and garden plants with the water to fight aphids and pests. You can use or add Garlic too as it repels bugs as well.