[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?

[Fleecewife]

White fly are tiny delta-wing flies which usually fly away in a cloud when you disturb them (and don't do much damage), so more likely to be mealy bugs - maybe.  They have a thick waxy coating so you need something to break through that.  It might be better just to scratch them off if there are not too many, or someone else may have some more ideas.

[BML]

I keyed, "Mealy Bugs" into the Web and it does not look like them but someone told me it may be "flea beetle" so I keyed that into the Web and selected, "Images".  The pictures clearly show it is flea beetle that did the damage. 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 some advice on how to treat the seedlings so any advice will be welcome.

[Fleecewife]

Flea beetles are fun the trap - get a small plank and coat it with engine grease, then pass it just above the plants.  The beetles will jump up as you disturb them and get stuck to the board.  You could do it with yellow sticky traps too if you have them - I won't have yellow sticky traps on my place as they trap beautiful things like bees, hoverflies, ladybirds etc - all the goodies as well as the baddies.
Another way to get the flea beetles, if you have children, is for them to catch them and squash them.  One of my sons loved to do that - and no, he hasn't grown up into a serial killer