I've noticed something very interesting... I have some kale (a brassica, like cabbage, but grows on a stem that can get tall) planted in two locations. The first patch is down in the bottom garden, exposed to rain, elements, birds, insects. The second lot are in pots, by the back porch, and are where I can keep an eye on them.
Guess which get eaten most by caterpillars?
I have a thought that it's a case of small birds actively keeping down any grubs on the lot that's further away - birds that would keep away from the house. Alternatively, there are a few other, companion plants that are in that bed - either keeping bugs away or convincing them that they are better eating.
It's good to know, though, that there are alternatives to pesticides... Apart from health concerns with using them, if you can't make something that you depend on - well, you better hope you don't need it, or can find something else to use in its place.