Ok strange but it works old and tried methord
When planting a cabbage family useing a dibber drop an inch cube of rhubarb into the hole first.
This is ment to stop club root forming and it dosent hurt the cabbage.
I did this with my last greens I put in! Left some without, so will let you know how I get on, so long as the slugs don't get to them before me ;D
Doris dont be mean buy your slugs some beer and let them enjoy their short life then watch the birds try to fly while under the infulance ha ha