I don't know what they are but you plant other plants around your plants that ward off the pests that are eating your veggies!
These other plants usually encourage insects and other preditors that then eat your problem pests.
I know that beer in bowls bureid up to the lip encourages slugs to drown, & roasted crushed egg shells also deter the snails and slugs.
Try an organic grow your own veg site, sure it will have all the answers!!
Hope this was of some use!