There is an old snowball bush here, snowball viburnum (as opposed to the kind that is actually a hydrangea); it belonged to my husband's grandmother, and has bloomed repeatedly for decades.
The problem was, it was covered with little green aphids, which meant I could never pick the blooms and bring them inside, because of my house plants. But they never seemed to harm the plant, and short of spraying (and killing the bees), there was little I would or could do.
some years back some new japanese ladybugs were released into this country, and I suspect there are few people who have not been treated to them in the fall, marching across the computer screens, queueing up for snacks (I use apple sections) in winter, and in some cases coating, literally, doors and walls and porches.
They LOVE little green aphids. The summer after the new ladybugs arrived the little green aphids were gone, and haven't been seen since. Now it gets interesting. Two years ago I noticed my nasturtiums were covered on the underside with smeary black microscopic aphids that looked more like soot than bugs. yueuuuwww. Then I noticed that the snowball bush was too. within a week the fifteen foot high plant became a skeleton, all the flowers gone, and the leaves just totally destroyed. I sprayed the ground under the bush, cut it back, and it seemed okay last year.
It has just breathed its last. The black aphids are back, the last of the flowers has turned brown, and the leaves are gone, all in three days. Tomorrow we are uprooting it and putting it on the brush pile at the end of the field. What I think happened (and this makes sense, clear to the ground) is that the little green aphids had a kind of symbiotic relationship with the snowball bush, and the balance was even. When the thousands of new japanese ladybugs arrived, they took out the green aphids, leaving the bush open for attack from anything out there. What was out there were the utterly devastating black aphids, who have no qualms about the bush, and then move on to other things.
The balance has been disrupted, and I'm not sure replacing the bush is an option.
Most of our problem plants and insects come from the far east, where over there they are part of a very different organic structure, and are kept neatly in their own niches. When they arrive here the climate is different, as is the soil and the way we grow our plants and crops. Fresh meat, they gurgle. oboyoboyoboy. Our own native plants have their own relationships with insects and the soil, and when something new shows up they have no defenses against it. Japanese beetles, asiatic beetles, (not to mention the Asiatic lilies we buy apparently just to feed them), gypsy moths, etc etc.
I think, on a very small scale, this is what we keep doing on a very much larger scale, and never learn from.