Friday, September 7, 2018

The Aster Yellows Blues by Carol King

Echinacea varieties, photo by Donna Duffy

My latest indignity in the garden, (does it never end) is aster yellows in a cone flower, Echinacea purpurea.  A couple of years ago I noticed a Dr. Seussian blossom with funny shaped green things coming out of the flower. My research led me to this condition called aster yellows.

It is a disease carried by the aster leafhopper (Macrosteles quadrillineatus). Aster leafhoppers overwinter in northern Texas, Oklahoma and Arkansas. Come spring, they want to get out of that heat and humidity and so they hitch a ride on the wind and end up in Colorado (and Kansas, Nebraska, the Dakotas, Minnesota, and Wisconsin.) The leafhopper is infected with this bacteria-like creature and transmits it to susceptible plants. It is also called witches broom, purple top, apical leaf roll, blue stem, bunch top, haywire, late breaking, purple dwarf, and yellow top (English) and is found all over the world.

Aster yellows affect 300 different species that represent more than 40 families of plants. This list is not complete but as you can see, dear gardener, it can affect much of the garden. The saddest note of all is that it can totally affect the potato chip crop. Horrors! 

Crops: broccoli, buckwheat, cabbage, carrot, cauliflower, celery, endive, flax, lettuce, onion, parlsey, potato, parsnip, pumpkin, red clover, salsify, spinach, strawberry and tomato.

Flowers: aster, anemone, calendula, China aster, chrysanthemum, cockscomb, Coreopsis, cosmos, delphinium, daisies, echinacea, gaillardia, hydrangea, marigold, periwinkle, petunia, phlox, scabiosa, snapdragon, statice, strawflower, veronica, and zinnia.

Weeds: cinquefoil, daisy fleabane, dandelion, horseweed, plantain, ragweed, thistle, wild carrot, and wild lettuce.

Once infected, there is no cure. Diseased plants should be promptly removed and discarded to reduce further spread. So, if you notice this condition,  go pull up and destroy your cone flower and have a sad case of the aster yellows blues.

Here’s some more information from CSU's Planttalk on Aster Yellows.