Big or small they always seem to come in plagues.

Hand catching them in the early morning or late afternoon can improve the situation. My neighbour used to catch mine to feed her frogs and word seemed to get around. A week or so later they were much more scarce.

Garlic and chilli based sprays can deter them to a point. If you need to wage war, the best is Carbaryl. But it is VERY VERY BAD. It works by affecting the nervous system, causing uncontrolled nerve movement, spasms, paralysis, convulsions and death. Do you really need to be spraying that?