This is a close-up of an Aster Yellows Disease effected Echinacea 'Magnus' plant.  The flowers have all turned green and are distorted.  It is caused by phytoplasma which is similar to a virus.  Not much can be done for this except to take out the plant and put in your trash-can and NOT in your composter, or out with the other plant material which will only spread the disease.  The disease is spread by leafhopper insects that suck out the juices, taking in the disease, only to spread it to other plants that it subsequently feeds off of.  I have lost a few Echinacea's over the years.  For more information go to: Missouri Botanical Gardens - Aster Yellows.

This is an Aster Yellows Diseased Echinacea 'Magnus'.  Notice that the flowers have moslty turned green with  floret's of smaller flowers emerging out of the cone.  Some of the flowers still have purple petals.

This is how a healthy Echinacea purpruea 'Magnus' should look.  Notice the orange center cone and clear purple petals.