The more we plant something, the more something comes along to eat it. Usually something buggy.
In the case of coneflowers (Echinacea), this green, tufted centre in the centre of the disk is a sign of some undesirable noshing going on. The culprit is an unnamed type of eriophyid mite, a breed of microscopic, sucking critter responsible for a host of plant problems, from leaf blistering to bud galls.
A mite is closer to a spider (or scorpion or tick) than an insect, and very, very tiny. But, boy, are there a lot of different kinds. The 50,000 that have been identified are said to be only about 5% of all mite species, and the one that caused the deformity on this coneflower is one of the unknowns.
Isn’t nature amazing?
Prevention is hard for the home gardener. And there’s not much you can do to treat them once the damage is done, unfortunately, except perhaps remove and destroy the damaged plant part.