Handpicking: We can take advantage of the homing and nocturnal habits of snails by going out at night, about 20 minutes after dark, with a torch, or early in the morning. The snails can be seen coming out of hiding, following the silvery trail of the lead snail or the silver highway from previous treks. Although time consuming , this technique can be very effective if done regularly. Pick daily at first until the population is reduced, then as needed, at least once a week. When disposing of snails caught in traps or picked by hand, crush them and dispose of their bodies, as mature eggs in the snail body may still hatch. Feed them to chooks or if brave, clean them by keeping them in a container of plain flour for a day or two and eat them yourself. Snails are 12-18% protein, low in calories and rich in minerals.
Management Barriers: Any dry dusty or sharp material can be a barrier to snails. Hydrated lime, wood ash, sharp sand or similar materials are useful. A band 20cms wide and 1 cm high is required. The effectiveness of barriers is reduced when wet so locate them away from watering points. Snail fences may also be made from galvanised metal, window screen wire and similar materials. 30 mesh copper screens can be nailed to trees to prevent climbing, or steel wool can be wound around trestle legs in glass houses. Electric fencing for snails is simply made and has the advantage of being more effective when wet!
Repellents: Wormwood, prostrate rosemary, acacia bark, and oak leaves are disliked by snails and make good repellent mulches. Wormwood is also effective as a spray. Stinging nettle as a companion plant also works. Basil and rue may also have some use as a repellent.
Biological Controls: The viscid slime that slugs produce repels many creatures, however toads, bullfrogs, lizards, some birds, turtles, small native marsupials and some other creatures may eat snails. Some flies lay eggs on snails and the young become parasites.
Poultry can be effective snail controllers, duck have a good searching habit, probing under plants with their beaks, but chooks and geese are also good. Feed poultry on greens before releasing them into the garden, they will then be seeking a protein diet. You may need to control their access to seedlings.
Many small ground dwelling arthropods will attack small snails, before the shell hardens or the slime layer gets too thick. They may also eat eggs. Rove beetles or ground beetles (the long black one that is often found in large numbers around compost) are very good, as are centipedes.
Poisons: A combination of the above methods will usually work. Don’t expect just one method to be enough.