Distorted and strange flowers? It could be Aster ylorus disease
The large purple flower heads I was expecting to see have been replaced with flowers straight out of a Dr. Seuss book. Lush green “petals” surround bright green cones. Even stranger is that in some locations, the leaf-like petals have been replaced by extra flower stems – also diseased green and badly disfigured.
At first I thought it was just a genetic anomaly. Looking deeper, I realized the news was much worse – a classic case of starburst jaundice.
Star yellows disease is caused by phytoplasma – a special type of bacterial plant pathogen – which is transmitted by leafhoppers. According to John Bonkowski, a plant disease diagnostician at Purdue University Plant and Pest Diagnostic Laboratory“What usually happens is there’s phytoplasma in the leafhopper’s gut. So, while feeding, the leafhopper sticks the mouthpart into the leaf and sucks out some of its contents. Sometimes they also excrete saliva, and the phytoplasma comes out when they do that. It gets into the plant.”
Phytoplasma is a type of parasite, which is a bacterium that lacks cell walls. As such, they cannot live abroad on their own. “They have to be inside the host,” Bonkowski says. “That’s why they’re carried by insects.”
Echinacea plants are among the plants most affected by yellow star disease. However, marigolds, zinnias, chrysanthemums, and chrysanthemums are some other susceptible targets.
Symptoms of the disease
Once an infected leafhopper transmits the pathogen’s phytoplasma to the plant, the entire plant is systemically affected. “It will be throughout the plant,” Bonkowski says. “Phytoplasma can affect the balance of hormones in the plant, which is why you end up seeing these very specific symptoms in coneflowers, zinnias and other asters.”
“The flower parts will start developing leaves,” he adds. “So, in the case of echinacea, you have the cone itself — the prickly part — and it will actually start forming clusters of leaves.”
In general, plant growth may be very stunted and small. “There may be more stems than the average plant produces,” Bonkowski says. “You’ll have these branches that are very green and maybe smaller than you would expect from a typical flower. The big thing is that the hormonal balance is disrupted, and you get these weird plant growths because of that.”
When it comes to eliminating star yellow in affected plants, there is really no good cure. Moreover, simply trimming it to the ground is not enough. “Stellate yellow phytoplasma will not survive in infected plant debris. But it does Can “It lives in the crown and roots of infected perennials,” Bonkowski says.
If the bacteria that caused starburst yellow are allowed to remain in the roots of perennials, the growth of subsequent new plants may be affected. Your best bet? Get out your shovel and start digging. “It’s best to remove any kind of (infected plant) material, because (bacteria) can be everywhere,” he says.
“It can get really bad if there’s a big infestation of leafhoppers and they’re transmitting (the disease),” Bonkowski says.
However, trying to control the spread of star yellow by killing leafhoppers is not practical. “Even trying to manage insects themselves, they are everywhere,” he points out. “So, that’s not usually possible in a home garden, because they can come in from somewhere else nearby. Even if you apply a preventive type of insecticide, it may kill some of them, but more of them may have the opportunity, after using something, to come in and feed on Plants again.
Pesticides are also a problem because they kill indiscriminately. This means you could end up harming valuable insect pollinators, not to mention some beneficial insects that naturally feed on leafhoppers.
Once infected plants are dug up, they should be carefully disposed of. To be on the safe side, you can store diseased plant material in bags and dispose of it. (Just be sure to check local laws first, since it’s illegal to dispose of residential plants in some areas.) Alternatively, you can dig a deep hole in the ground and bury the plant droppings.
Last but not least, check any remaining plants periodically for signs of new infestation. Pull and dispose of additional infected plants as needed.