Witch hazel gall cones (aphids?)
got a quickie for you. i have a witch hazel in the backyard. i've noticed the past couple of years that my specimen isn't growing very much and every year, there are a ton of wart-looking cones ("galls") popping up on the plant, which are apparently common and related to aphids. If I squeeze the cones, it seems to kill them, but the leaves obviously don't recuperate.
Generally, I would consider this a feature, but I wonder - should I be treating this/killing the aphids? If so, how? Is this condition injuring the plant at all?
Here's a picture in case anyone is interested. If you cut the cones open, there are insects inside. One of ths strangest things I've ever seen!