What caused the little holes?

[BML]

This is the first time I have attempted to grow what I will call, "Spring Cabbage" and it doesn't look as though there will be much to eat. I started the cabbage seed off in the green house and pricked out the seedlings into pots and waited for them to grow large enough to plant out into the garden. I am very new to vegetable gardening so when I saw that the seedlings had little holes in them I thought it was caterpillars and it was only when I started to plant the seedlings out today and picked the pots up to tap to shake the seedlings out that I found very small little white things cunningly secreted underneath the leaves which moved when I touched them. As a result I sprayed the underneath bits of the seedlings before I planted them.
I have one question: Do I have to continue to spray them and if so for how long or is there another method of control?

[Francis Barnswallow]

Sounds like aphids to me. I use an organic soap insecticide when I first see those little buggers. Usually takes a few days to get rid of most of them.

[BML]

Would these be responsible for nibbling the small holes in the plants?

[DoubleDogFarm]

If the leaves are riddled with holes like a blast from a shotgun, you may have flea beetle.

Eric

[BML]

I keyed, "flea beetle" into the Web and selected, "Images" and the pictures clearly show it is flea beetle that did the damage so thank you very much. The strange thing is that one of the set of trays of one type of Spring Cabbage was attacked and another set of a different sort of Spring Cabbage about a yard away was hardly touched. Now I need to find something to treat the seedlings with so any advice will be welcome.