The first time I came across Asters Yellows Disease, I was living in St. Louis and it caught me off guard. “What is wrong with the purple coneflowers?” I thought, as I examined the seemingly healthy plant with strange, green deformed flowers.
Thinking it was simply a genetic mutation; I trimmed off the ugly stalk and hoped it would grow out of the deformity. To my dismay, it appeared upon re-flowering; eventually spreading to other once healthy coneflowers in different locations throughout the yard.
Every year I look for and destroy any diseased plant I come across, yet it still shows up on at least one plant in the gardens a year.
Asters Yellows Disease affects some of the best cultivated and native plants of the Midwest including Echinacea, and Rudebeckia; the later a genus exclusive to North America.
Rudebeckia fulgida var. sullivantii ‘Goldstrum’ commonly called Black-Eyed-Susans, is one of the most popular perennial plants planted in perennial sun gardens.
Asters Yellows Disease is very common throughout the Midwest; in the native habitat of these beautiful herbaceous plants, which are pollinator magnets in late spring and summer.
Asters Yellows Phytoplasma, is a bacterium without a cell wall and develops in the phloem of plants. Typical symptoms include witches brooms: abnormal groups of deformed branches or growth.
The disease symptoms differ depending on the plant host, often causing yellowing of foliage and deformity of normal growth.
How does it spread?
This disease is often carried to Missouri by migrating leaf hoppers from the southern states. Asters Yellows Disease is vectored, or carried by leaf hoppers from one infected plant to another, often making this disease hard to eradicate from a garden location.
Compounding the problem is that once picked up by the leaf hopper, it is essentially vectored to susceptible plants not once but continuously, as it feeds on the sap of plant hosts; rapidly spreading the disease.
Not only can strains of this phytoplasma infect cultivated plants such as coneflowers and zinnias, it can also target and reduce production of many more plant families including common vegetables like carrots, lettuce and broccoli.
Like I mentioned weeks ago to prevent squash bug damage, experts endorse tightly covering vegetable plants with floating row covers can limit leaf hoppers, and therefore the disease pressure on crops.
There is no cure for Asters Yellows Disease, and like plant viral diseases, it is recommended to dig out and destroy infected plants as soon as the disease symptoms occur. For home gardens, this is the easiest and most useful control method.
The Missouri Botanical Garden recommends removing weed hosts the disease can infect and overwinter or nearby, to help limit disease pressure.
Page 2 of 2 - Since this disease is more prevalent in cool, wet weather, keep an eye out for this common garden disease this spring and summer.
Remember that monitoring, preventative measures and quick action to remove infected plants, is the best way to stop any disease from overtaking your garden.