I posted a little story about some ragweed plants covered with aphids a few days ago. The ragweed plant has since recovered with few signs that the aphids were there in the first place.
If you look closely, the little red bits seem to be the remains of aphids. I looked at the plants that formerly had aphids, and none seemed to have any living adults anymore. The plants are healthy and robust, and none of the ragweed plants nearby seem to have infestations of aphids.
So in case you were worried, the ragweed in Iowa is doing quite well, thank you.