You can use the organic Dipel or Thurgicide. It is a bacterium specifically for caterpillars. It won't harm anything else.
The problem with using any pesticide, while it may seem the easy way out. In the long run, you end up spending more time and money. A broad spectrum insecticide like Seven will kill a lot more than the bugs you are targeting, but it is also harmful to beneficial insects that would otherwise control the bad bugs and is also toxic to bees. If you kill off the good bugs, you end up on the pesticide treadmill, because unless you continue to spray, the bad bugs will keep on coming back without natural controls to keep them in check.
While you are killing the caterpillars, the moths that really don't live on the plant, will just come back and lay more eggs.