I don't think it's possible to delete a photo from iPhoto. No application in the App Store have access to deleting photos in your devices camera roll. You can always delete photos from the built-in Photos application.
But I have found a simply way to do it... And that can help someone else:
After imported selected pictures with the camera connector, just go to the "last imported pictures" album, then you can select pictures you want to delete from ipad...