Lures are great but keep in mind they use a pheromone lure and can bring not only the ones in your yard but from miles around making a bigger problem. If you see a surge in numbers take down the lure and replace it with this:
Take a plastic dish or shallow cup spray paint it bright yellow. Coat...
Sound like you have lily leaf beetles. The larva is what actually destroys the plant. They can consume and entire plant overnight. The gooey ball that you are seeing is actually the larva which encases themselves in the goo to protect them (it's actually there poo). Look around for a bright red...