Leafhoppers are one of the largest families of plant-feeding insects. There are more species of this pest, than all species of birds, mammals, reptiles, and amphibians combined.
Common Sense Methods of Pest Suppression
Control weeds to avoid breeding grounds, and wintering space.
Follow Crop rotation guidelines
For indoor plants and seedlings avoid putting susceptible plants close to windows, vents or doors, Bugs don't knock before they enter, if they did you probably wouldn't hear it anyway.
Destroy and discard infected plant material
Garden Web - Leaf Hoppers
American Horticultural Society Pests and Diseases: The Complete Guide to Preventing, Identifying and Treating Plant Problems
Insect Guide - Leaf Hoppers
Other Common Garden Pests