Ahh, snails. The nemesis of many a gardener.

The little buggers have been known to occasionally attack my cacti, but by-and-large will generally leave them alone. However, some plants seem to be constantly munched on by slimy critters, specifically one species of Opuntia (don't ask me which one, I found it growing in my compost heap!), Pereskiopsis spathulata and Echinopsis backebergii. Anyone know why this is so? Are some of my plants particularly delicious?

Lachy,

All of your plant are delicious to snails and they will eat any of them given the chance. The issue is some of the plants are harder to attack than others, some have too many spines or are a difficult shape but the most common reason is the skin is too tough / thick. Thick skinned plants are harder to munch through and thus are targeted less, it does not mean they will never be eaten they are just harder targets.

I have heaps and heaps of problems with snails at my place.....I hate them.

HN

Crackle crackle, squish squish.

I learnt this the hard way, they love most of my trichos.
Lesson of the day: dont put tricho pots next to vege garden.

Lachy,
You may want to consider putting down some snail pellets around your plants to kill the snails (and slugs too). I have used these with good results. Mind you be careful if you have pets/small children around which may frequent the treated area.

Cheers for the suggestion, Lewis. I generally dislike using any sort of pesticide in the garden however I have found some bait that is supposedly "pet safe". I've also moved some of the more attacked cacti to a place that should be less accessible to slimy critters.

My only gripe about snail bait is that if you have bluetounges in your area and they eat a baited snail it will digest and kill them. The above mentioned pets and children is not such a big issue as stated you can get petsafe versions.

I always found moving them up off the ground and REMOVE! any uneeded shady plants/ ground ferns or other such plants they will be lurking in away from where you grow your cacti. luckily I faced that problem last year. and now I have a great baren backyard to teraform into a giant cacterium. with not a snail in sight.... however now im facing burn issues as I have no shade.

You cant beat em.....so SQUISH EM!!