Yellow Asters?

Asked September 29, 2020, 1:39 PM EDT

We had clear infections of yellow asters on coneflowers earlier this year. We are now seeing other symptoms on the coneflower disks/cones and are wondering if they are indicators of yellow asters or some other pest or pathogen.

Baltimore County Maryland

1 Response

We do not see clear signs of Aster Yellows on these plants, so another cause is likely. Flowers can become deformed when they are developing by a tiny mite, which can cause symptoms very similar to the Aster Yellows pathogen. Various other chewing insects (caterpillars, beetles, earwigs, etc.) can also damage petals and cones, leading to aberrations in the flower shape. You can simply trim these off if they are an eyesore, but otherwise it should not impact the overall health of the plant.

Here is a gallery of some of the most common symptoms (on blooms) of Aster Yellows in Coneflower, with a comparison to mite damage in one image: