Coneflower seed heads

Asked August 28, 2020, 3:37 PM EDT

Hi, What is happening to my Coneflower seed heads? About 25% of my Coneflowers have this happening to them (see picture) Do you know why this is happening? Is it anything to worry about?

Howard County Maryland

1 Response

These appear to be symptoms of Aster Yellows, a virus-like pathogen which affects daisy-family plants such as these along with many other garden plants and weeds. It is transmitted by sap-sucking insects called leafhoppers. Leafhoppers are common garden pests but their control is quite difficult, especially on plants such as these that have good wildlife value (and therefore should not be treated with insecticide).

Aster Yellows is not curable and will eventually kill a plant. The affected plants (roots included) need to be removed and disposed of (do not compost).

The pathogen is not in the soil itself, so you can replant safely, though there is a risk new plants will contract the same pathogen if they are vulnerable species and are feed upon by infected leafhoppers. To reduce this risk, make sure the area is weed-free and be vigilant for symptoms appearing in any nearby plants, removing them as needed if they do manifest.

These pages provide more information on this disease and a few look-alike conditions:
https://extension.umd.edu/hgic/topics/aster-yellows

https://bygl.osu.edu/index.php/node/1634

https://wimastergardener.org/files/2015/12/aster_yellows.pdf

Christa