If you're a lover of coneflowers (Echinacea sp.), then this is your time of year. The coneflowers are blooming beautifully in many gardens across Northern Illinois. Some gardeners have made note though, that their purple coneflowers in particular are looking a little peculiar this season.

Some have noted that they are getting very little flowering and the flowers they do have are partially to completely green. Several flowers can have odd green growths sticking up from the center of the blossom as well. These are all symptoms of the disease Aster Yellows.

Aster yellows is a chronic, systemic disease that affects over 300 species in 38 families of broad-leaf, herbaceous plants. Members of the aster family (Asteraceae), such as asters, marigolds, Coreopsis and purple coneflower are commonly affected by this disease. Infected plants are typically stunted and twisted, with foliage that is yellow or red. Floral parts that are normally brightly colored may remain green, and petals and sepals may become puckered and distorted. In purple coneflower, secondary flower heads (often in a cluster) may emerge from the primary flower head.

Aster yellows is a disease that is different from many of our common fungal, bacteria, or viral diseases because it is caused by a tiny bacteria-like organism known as a phytoplasma. Phytoplasmas live within the phloem (nutrient conducting vascular system) of plants. The aster leafhopper (Macrosteles fascifrons), a common insect, moves the aster yellows phytoplasma from plant to plant. Every time the leaf hopper feeds, some phytoplasmas are released into the new plant, starting a new infection.

Unfortunately there is no known cure for aster yellows. Infected plants will not necessarily die from this disease, but they should be removed immediately so that the aster yellows phytoplasma cannot be spread from infected plants to other non-infected plants in the area.