Cabbage root fly?

[Kea]

Some of my cabbage seedlings which are still at home in pots wilted and I found white grubs round the bottom of the stem and very little root attached in fact the two affected just separated from what was left of their roots. I assume this is cabbage root fly.....and I didn't even get them in the ground yet :'(.
What is the best protection for the rest?...the ones in the ground have there collars, though now I'm hoping they weren't affected before I planted them out.

[Kea]

[Kea]

Anybody?

[telboy]

Kea,
Try soaking around the plant bases with 'Bugclear'. After a day or so a liquid feed boost , you may save the affected plants & give any not affected a lift. Must admit, it seems late for cabbage root fly.
:(

[Kea]

Just found this useful site http://www2.warwick.ac.uk/fac/sci/whri/hdcpestbulletin/

though I perhaps might need to repost in new thread.