My Rose of Sharon's were completely infested with aphids. I've never seen anything like it. Gross! It was time to cut them back, so I did a hard prune and it got most of the aphids, but I wasn't able to bag the limbs. Had to put them directly in the trash bin. I see there are still a few aphids on the trees and some on the trash bin. Should I spray trees and bin with neem? I read I can make my own neem soap spray. Is this advisable?