Diatomaceous earth consists of very sharp crystals and it has been shown to be a very effective substance to control pests go the garden ranging from aphids to slugs. It also comes dirt cheap, go my place, it costs $0.2 per kilogram. It has am additional benefit in the fact that its surely organic.
Diatomaceous earth is very cheap and very effective against bugs and sometimes snails. The problem with it is that you have to reapply it every time it rains which can be a hassle if you live in areas where there are afternoon showers almost every day. I don´t use it to sprinkle over the entire garden, I instead use it around ant holes and also just around certain plants that are susceptible to ants or slugs ( cabbage, brocoli etc). But in my opinion, the better option is to interplant onions or garlic throughout your garden, most ground insects hate them. I never plant my onions in rows, instead I have it scattered all over the place.
