A good strong household ammonia solution with some hot pepper sauce in it usually does them in quickly. Remember that they are living in the soil, so pour it on the ground around the base of the plants. This is very hard on worms too tho so be prepared with some nice cool water to rinse off the worms if they come up too. Tobacco water works fairly well too but I would make it part of the above solution if used. Just soak some chewing tobacco, cigarette butts, etc, in some hot water until the water is cold. Strain it off and add to the ammonia/ hot pepper solution.