That would be the beet leafhopper. It spreads a fatal virus called curly-top to many plants, but mostly beets (duh), peppers, and tomatoes. Here are the results of two infections:
The infection mimics drought, but watering won’t cure a virus. Nothing will. Pull plants like this out of the garden and put them in the trash. Do not compost them, for these leafhoppers can overwinter in your yard–composting stops during the winter, remember? Here is a link to an excellent article on curly-top virus.