If you look at the plant you'll see the black spots they are leaving. These insects cause tremendous damage. I tried catching the insects into a jar but they have wings and I was unable to catch them. They escaped and fell to the ground after using their wings to avoid being caught. For some reason after visiting the park a second time today - to try to catch the insects. The plant looked like a whole different liatris plant, it was wilted, as though it had been replaced by an even more damaged plant. I'm second guessing myself, so I'm going to examine the plant again tomorrow. The only damage to the first plant was at the top as shown in the picture, but the second plant had tiny dark spots all over it.
Someone has been stealing plants on a regular basis from the park. I don't know about the plants planted by others in the other areas of the park, but mine which are in the small field by the gate, have been.
This was at the top of the plant
Four Lined Plant Bug - Poecilocapus lineatus