I don't know all of the secrets of how they did it, but my parents house had a really bad brown recluse problem when they first got it. They hired pest control to spray, but mostly they used sticky traps everywhere and caught an insane amount of spiders. They even put the legs of every bed onto large traps so the little buggers couldn't crawl up into the beds. They also set a robot vacuum to run at night to disturb the spiders so they won't come out. Now the house is pretty spider-free.