This nematode business seems to be a very expensive method of attempting to control molluscs. I find that it is just as good to go on slug and snail hunting expeditions every evening, gathering them up and giving them a last 'party' of old stale beer, and they go out fighting drunk, happy and lose ANY sense of direction for finding their way back to my allotment ! Failing this, I would get a badger and let it loose around the garden. The pet badger I had, was quite fat on the resulting feasting, but also dug up with scientific precision all the bean and pea seeds so geometrically placed ! You pays yer money and takes yer chances.