Aster yellows

Definition

A chronic, systemic plant disease caused by phytoplasmas in the 16SrI group (primarily 'Candidatus Phytoplasma asteris'), transmitted by phloem-feeding leafhoppers. Infection produces diverse symptoms including phyllody (leaf-like floral structures), virescence (greening of petals), chlorosis, stunting, and floral sterility across 300+ host species in 38 plant families. The primary vector, the aster leafhopper Macrosteles quadrilineatus (Cicadellidae), acquires the pathogen during feeding and transmits it persistently, making this a model system for studying insect-vectored phytoplasma ecology and a significant concern in carrot, cereal, and nursery crop protection.

Etymology

From Aster (the daisy/aster family Asteraceae, principal host group) + yellows (the yellowing chlorosis characteristic of infection)

Example

In carrot fields, aster yellows causes severe economic losses when Macrosteles quadrilineatus populations surge; integrated management combines monitoring of leafhopper migration with targeted insecticide applications, as no curative treatment exists for infected plants.

Synonyms

• AYP
• aster yellows phytoplasma

Related Terms

• phytoplasma
• leafhopper
• Macrosteles quadrilineatus
• Vector
• phloem
• phyllody
• virescence
• persistent transmission
• plant disease ecology

Usage Notes

The term refers specifically to the disease syndrome, not the pathogen itself (properly 'aster yellows phytoplasma' or 'Candidatus Phytoplasma asteris'). Multiple distinct phytoplasma strains cause similar symptoms; molecular typing is required for precise identification. The disease exemplifies circulative-propagative transmission: phytoplasmas multiply within the leafhopper vector and persist through molts, though they are not transovarially transmitted. Contrast with viral yellows diseases (e.g., barley yellow dwarf virus, also aphid-vectored) and with phytoplasma diseases transmitted by different vectors such as planthoppers or psyllids.