Hello. Slugs and snails don't like to crawl over coffee grounds, egg shells and copper. You can put rings of protection around your plant. Please don't kill any more spiders, they are one of the best defenses against bugs They don't eat plants and can only live where there is food enough for them. They see very well and are quite smart. Caterpillars can't walk on water. If you are in pots get a large tray, put some rocks in the bottom so your plants don't sit in water, and fill with water. Good Luck. Chuck.