I don't know how true it is or even if it works but there was an article in in our local newspaper that said to get rid of insects you should put onion and garlic in a spray bottle and spray your plants. Has anyone heard of this?
I do use it in my garden, if I start having pests and have generally had decent results with it. It is not going to make sure there is never an insect in your yard again, but you don't need that. It does seem to help.