Here are the Ten Commandments of pet and wildlife protection when you use slug and snail poisons.
Never rely on poisons as your sole form of snail and slug control. No poison will ever be more than about 90% effective. If you try to rely on poisons for 100% of your pest control needs you will probably try to use more and more, with more and more collateral damage to wildlife and pets, but you will never completely control slugs or snails with poison alone.
Use poisons when you have massive infestations of slugs and snails, not when you have just a few slugs and snails. Poisons are usually for killing large number of pests quickly, but they are not as useful for long-term control.
Use the right poison at the right time. Metaldehyde poisons are only truly effective during hot and dry weather. If a slug or a snail eats metaldehyde and then gets rained on (or chances under your watering pail or sprinkler system), it will be stunned but will probably survive. Rain, wind, animals, and small people may move your iron baits so slugs and snails never encounter them.
Make sure poison baits are attractive to slugs and snails, not to pets and wildlife. Passing pets and wild animals tend to ignore single pellets of poison bait. They will stop to investigate small piles of poisoned food, and usually will taste it. Make sure you put out any poison slug and snail baits at a safe distance from outdoor food and water bowls for your cats and dogs, and don’t scatter cereal-based baits around the bird feeder or bird bath.
Remember that copper compounds and water are a bad combination. Bordeaux mixture and copper sulfate are used to stop the fungal infections, blight, and mildew that kill trees and secondarily feed slugs and snails. Always coat a layer of Bordeaux mixture with a layer of latex paint so it does not leach off the tree and into the nearby water supply. Bordeaux mixture and copper sulfate are both highly toxic to fish and other aquatic wildlife.
Never use carbamate (Sevin dust) to control slugs and snails on flowering plants. It is extremely toxic to honeybees. It also kills the mites and parasites that keep snails in check.
Use metaldehyde only at ground level or as a drench for potting soil you use for potted plants. Metaldehyde is only moderately toxic to honeybees, but it kills many other kinds of beneficial insects in the garden.
If your climate permits, plant exotic vegetables that are edible for people but toxic to slugs and snails. These include striped eggplant (kantakari, Solanum xanthocarpum). Jicama is also potentially toxic to these pests. Or try growing an ornamental plant that is potently toxic to slugs and snails like pokeweed or gopo berry (Phytolacca dodecandra). All of the euphorbias are also toxic to snails and slugs.
Just as you limit your use of pesticides, limit your use of herbicides. Pull weeds. Don’t spray them. Exposure to weed killers usually has little effect on snails and slugs themselves, but it encourages the growth of their parasites, some of which can also infect people.
Keep in mind that all common slug and snail poisons that except iron are toxic to some forms of wildlife and unhealthy for the people who use them.
Simon Mann is a "handy man" to have around the house. Although he was a trained carpenter he went on to become a VP of a construction company. Any pest or DIY problem you may have, he always seems to come up with the right solution.