These small garden snails have quickly established a family network in the tops of some Brussels sprouts plants. Snails often climb higher than slugs and, because they have their shells, they will set up camp and hide in the plants. When they do, the damage can be quite extensive, and in this way they can be more destructive than slugs.
For slugs and snails that are largely camping out at ground level, beer traps, eggshells and grit barriers, copper tape and so on can be effective ways to protect plants, but once you’ve got a few snails hiding out in the tops of your Brussels sprouts, those same control methods become redundant (although it is worth continuing to try and prevent further snails from climbing the stalks to join them!)
The only effective way to reduce numbers once they have climbed into your plants is, sadly, picking them out by hand. This is not a fun job, and if you don’t want to kill them you will have to be gentle with their shells! We try to pick our battles carefully – since the snails that are living in the sprout tops are currently not eating the sprouts themselves, we’ll probably leave them there. We can sacrifice the cabbage-like top, and as more damage is done and there is less remaining for the snails to eat, we may well cut off the entire top and add it to a compost pile, complete with the family of snails. They will be of more use there, helping the composting process, and hopefully the sprouts will stay intact.