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Aster Yellows

Aster Yellows

Candidatus Phytoplasma asteris

Phytoplasmaalso: Aster yellows

A disease caused by a phytoplasma, a tiny bacteria-like organism, that is spread by leafhoppers and twists plants into yellowed, stunted, weirdly deformed growth. Aster yellows hits a very wide range of vegetables and flowers, including carrots, lettuce, and many ornamentals, and there is no cure, so control means managing leafhoppers and pulling infected plants.

🔎 How to spot it

Look for yellowing, stunting, and strange distorted growth: clusters of spindly upright shoots, leaves that come in yellow or white, and flowers that are deformed, greenish, and leafy instead of normal. On carrots, look for yellow or reddish twisted tops, hairy secondary roots, and a bitter taste; on many flowers, look for green, stunted, sterile blooms.

🥀 Damage it causes

Infected plants are stunted, deformed, and unproductive, and the phytoplasma stays in the plant for life. Carrot roots turn bitter and hairy and lettuce fails to head, while ornamentals throw distorted, greenish, sterile flowers. Infected plants and perennial weeds become reservoirs that leafhoppers carry to healthy plants.

🔬 What causes it

Aster yellows is caused by a phytoplasma, Candidatus Phytoplasma asteris, that lives in the plant food-conducting tissue and is spread by leafhoppers, mainly the aster leafhopper, as they feed. The insects pick it up from infected plants and inject it into healthy ones, and the organism overwinters in perennial weeds, ornamentals, and the leafhoppers, often blowing in on leafhoppers from the south.

🛡️ Prevent it

Control the leafhoppers that spread it and keep down the perennial weeds that harbor both the insect and the phytoplasma in and around the garden. Remove and destroy infected plants promptly so they cannot serve as a source. Floating row cover can keep leafhoppers off vulnerable crops like carrots and lettuce, and some carrot varieties are more tolerant.

🧯 If it is already here

There is no cure, so pull and destroy infected plants as soon as you spot the telltale yellowing and deformity, and do not compost them, so leafhoppers cannot spread the phytoplasma from them. Manage leafhoppers on the remaining crop and clear nearby weed reservoirs. Prevention through vector and weed control is the only real handle on it.

💡 Good to know

The bizarre, almost mutant-looking growth, yellow leafy flowers, witches-broom shoots, and bitter hairy carrots, is the giveaway for aster yellows and sets it apart from ordinary nutrient yellowing. Because it rides on leafhoppers and overwinters in weeds, controlling the insect and removing infected plants and weeds are the only effective steps.

🌱 Plants it affects

235 plants in the library can be affected by this problem

African MarigoldAgapanthusAgeratumAlice du Pont MandevillaAmethyst Falls WisteriaAnemoneAngelique TulipAngeloniaAnnabelle Smooth HydrangeaAnnual VincaApeldoorn TulipApril Tryst CamelliaArizona Sun Blanket FlowerArugula🥕Atomic Red CarrotAugust Beauty GardeniaAutumn Joy SedumBachelor's ButtonBarbara Karst BougainvilleaBecky Shasta DaisyBee BalmBenarys Giant ZinniaBengal Tiger Canna🥬Bibb Lettuce🥬Black Seeded Simpson LettuceBlack-Eyed PeaBlack-eyed Susan VineBlood OrangeBloomsdale SpinachBlue Bird DelphiniumBlue Bird Rose of SharonBlue Fescue🥕Bolero CarrotBrunneraBurning BushButtercrunch LettuceButterfly Blue Pincushion FlowerButterfly Marguerite DaisyButterfly WeedCafe au Lait DahliaCaladiumCalendulaCalibrachoaCalifornia Giant ZinniaCalifornia PoppyCampanulaCardinal FlowerCarolina GeraniumCarolina JessamineChantenay CarrotChicoryClimbing HydrangeaClimbing Prairie RoseCocktail Vodka BegoniaColeusCollard GreensCoral Drift Groundcover RoseCosmic Purple CarrotCosmosCreeping PhloxCupani Sweet PeaDandelionDanvers CarrotDavid Garden PhloxDelft Blue HyacinthDenim n Lace Russian SageDragon CarrotDusty MillerDutch Master DaffodilEastern Red ColumbineEndiveEndless Summer HydrangeaEnglish LavenderEnglish Shelling PeaEvening PrimroseFanal AstilbeFeather Reed GrassField PeaFireworks GoldenrodFlamingo Feather CelosiaFlower Record CrocusFountain GrassFoxgloveFreesiaFrench MarigoldFriséeGarden GladiolusGarden PrimroseGarden SageGarvinea Sweet Glow GerberaGateway Joe Pye WeedGauraGlobe AmaranthGlobemaster AlliumGlossy AbeliaGoldflame SpireaGoldsturm Black-Eyed SusanGraham Thomas English RoseGrape HyacinthGreen Leaf Lettuce

For educational and informational purposes only. Disease management advice is general guidance drawn from university cooperative extension sources; always identify a problem positively and read and follow the label on any product before use, especially around food crops, children, and pets.