Yikes! That is a mess .. Using your sevin dust, you'll want to use a duster and make sure the 'cloud' gets under the leaves and on top of the leaves - the whole plant from top to bottom paying careful attention to the new growth. The dust only works if the critters crawl through it.
If you're not adverse to chemicals, then spray the plant with whatever garden pesticide you like to use ... again, you want to make sure the spray gets under and over the leaves.
It will still bloom if the buds aren't eaten but the damaged leaves will not fix themselves.
