I had used soapy water as a pesticide for indoor plants, but a few years ago, while kvetching about an outdoor infestation of box elder bugs (an example of the nasty things is pictured above), my next door neighbor Buzz, a retired bricklayer and WWII vet, suggested I use the stuff to tackle my buggy problem.
Any liquid dishwashing soap will work. Simply mix a couple of teaspoons to a gallon of water and hose the little bastar ...I mean, buggers. I use a 1 gallon weed sprayer to hose them, but any type of trigger bottle will work. Say an empty Windex bottle, for example.
(The squeamish may want to skip this part.) The soapy water doesn’t kill bugs instantly. It actually suffocates them, so it might not LOOK like it’s working, but don’t worry, after a minute or two they’ll stop moving. I usually do a couple passes of the infested area too, as the soap only kills what it can reach.
Although I use this technique primarily on box elder bugs–which have an annoying habit of flying at you instead of away from you, invariably getting stuck in your hair–I’ve noticed it works on other pesties too. Primarily lethargic fliers, like box elder bugs, and creepy crawlies, like ants and such. Plus, when you’re done spraying, your yard won’t smell like a toxic waste dump.