Several years ago I saw a TV show about this guy who had loads of black
widow spiders on his property. In my opinion, he devised a great way
to kill them. First he went out and bought a cheap can of hair spray.
He would go out at night when they are most active and hunt them using a
flashlight. He would then give them a shot of hair spray. When the
hair spray dries, it becomes stiff and the spider can no longer move,
thus it dies!

Rich