what is eating my swede leaves- any treatment ?

Most likely leaf beetles, if you mean lots of tiny holes in the leaf. If you pull a stick or a feather across the ground you should be able to see them jumping (they are tiny).
The organic way is with a grease band or something sticky, that you move over the soil. The beetles jump up and stick to the card.
You can spray for them, but we've found that an organic approach of flowers for predators etc. has almost eliminated them here. When we first sowed anything like turnips and cabbages the leaves were full of little holes. Now there's nothing.
If it's not leaf beetle, the most likely culprit is the ubiquitous slugs and snails.

I agree with Bertie and would not spray