Name: Carol Noel Hawaii (near Hilo) It's all about choices.
OK...so I've got an invasion of aphids on all my little starts of brassaicas (spelling looks off on that one) which, I am told means the 'cabbage aphid' has discovered me. I will spray....but is there any way to deter them???????
Aphids are opportunists who tend to pop up when the plants are otherwise stressed, in my experience. We had them come in (on cucurbits, so a different type) during the drought this summer. The best deterrent I know of is to keep the plants in top shape, though I don't doubt you're already doing that.
If you don't want to spray anything toxic, small aphid invasions can be knocked off the plants with a blast from a hose. But if you let them get too far so that the leaves curl up around them, it's almost impossible to get rid of them.