so my cosmos this year have been infested with what looks like a tiny little green bug of some sort and today I noticed that it had turned into black fuzzy caterpillar looking thing. Last year the cosmos bloomed over 3 feet. It was really tall but this year it has been infested. I mean there are so many of them; it's disgusting! Are they harmful? And what are they? Thank you so much.
Difficult to identify the insects specifically, but treat the plants with Neem OIl.
Neem Oil works as both an insecticide and fungicide and is safe for people, pets and bees.
Treat weekly until the infestation is under control.
Here are a few links with more information.