Good cheap homemade aphid killer. Kills on contact. Not a preventative though, so be prepared to use often. Edit: Word of caution. Don't tet this sit for more than a few days. I let it sit for more than a week and then sprayed my plants some more with it. The next day I noticed the leaves were starting to curl and had brown spot all over the underside. Pretty sure since it has the onion and garlic in it that bad bacteria start to form over time.