Flower Culture #4: Controlling Pests

I have to list three pests and one way to control them (other than chemicals).

1. White Flies: Properly space plants so the air can move around them.
2. Cut Worms: Home made cardboard collars that are stapled at the sides.
   
3. Slugs and Snails: Circle the inside of the flower bed that is being attacked with rough sand, ashes, or ground limestone.