|Head twisting from aster yellows infection on lettuce|
|Phylum:||Firmicutes or Tenericutes|
|Species:||Candidatus Phytoplasma asteris|
| Aster yellows
Aster yellows witches'-broom phytoplasma
Aster yellows is a disease caused by Aster yellows phytoplasma affecting several genera of herbaceous plants, primarily in the Aster family. The aster leafhopper vector, Macrosteles quadrilineatus, moves the aster yellows phytoplasma from plant to plant.
There are a range of characteristic symptoms which vary with the phytoplasma strain, timing of infection, plant species, temperature, age, and/or size of the plant. The symptoms can be mistaken for herbicide damage.
Symptoms include vein clearing until the entire leaf becomes chlorotic, stunting, deformation, virescence (greening of flowers), phyllody (development of leaf-like flower petals), reddening of foliage, reduced root system, and sterility. Aster yellows does not typically kill perennial host plants.
Initial vein clearing and chlorosis, followed by production of many adventitious shoots, with the tops looking like a witches’-broom. The internodes of such shoots are short as are the leaf petioles. Young leaves are smaller and dry up while the petioles of older leaves twist and break off. Any remaining older leaves turn bronze or red late in the season. Floral parts are deformed and roots are smaller, abnormally shaped and have woolly secondary roots. The carrot roots are predisposed to soft rots in the field and storage and taste unpleasant to the consumer.
No treatment is available to save a plant infected with aster yellows. It is best managed by removing infected plants from the garden to minimize spread.
Management of the insect vector is not usually feasible in a home garden.
- Bai et al. Living with genome instability: the adaptation of phytoplasmas to diverse environments of their insect and plant hosts. J. Bacteriol. 2006 May;188(10):3682-96.
- Davis, M. R. & Raid, R. N., eds. (2002). Compendium of Umbelliferous Crop Diseases. St. Paul: The American Phytopathological Society. pp. 58-59.
- O’Mara, J.; Bauernfeind, R.; Stevens, A.; Gast, K.; & Steven, S. (1993). Aster Yellows. Cooperative Extension Service, Kansas State University.
- Hudelson, Brian. (2006). Aster Yellows. University of Wisconsin Garden Facts.
- Agrios, George N. (2005). Plant Pathology. Burlington: Elsevier Academic Press. pp.691-694.
- Engelbrecht, C . (2006). Aster Yellows. Horticulture & Home Pest News. p103-104. IC-495(22).
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