Web Master:
Well Spud, slugs, snails and aphids are the biggest threat - the best way around this is to sprinkle slug pellets around your young plants. You can deter aphids with a spray of soapy water, but if they are already munching then a spray of Pyrethrum will send them packing.
But you could also have problems with birds while the shoots are young - with the solution here being bird netting, though once they are established you can take it off as they only seem to go for young and tender shoots.