Imagine a prank where somebody leaves a piece of cake in the middle of a huge poison ivy patch. If the school bullies try to steal the cake, they'll get an itchy case of poison ivy! Bruck's solution works the same way. He lures the weevils in with one of their favorite foods. When they come to eat it, they run into the deadly spores, with gross results.
A healthy larva looks like this:
But infected larvae look like this: