Cause: Aster yellows phytoplasma.
Occurrence: Aster yellows may occur during fall emergence, early spring growth or later in the growing season during heading and maturity.
Host Range: The disease has an extremely diverse host list, affecting more than 350 species in 54 plant families in the classes Liliopsida and Magnoliopsida.
Vector: Several species of leafhoppers (Family Cicadellidae); primarily Macrosteles quadrilineatus (formerly M. fascifrons) in North America.
Symptoms of aster yellows do not appear until 21 to 56 days after leafhopper transmission.
Key Symptoms:
· Young wheat plants are stunted and yellow (chlorotic), and may die prematurely.
· Older plants are exhibit chlorotic blotching especially on lower leaves, followed by general yellowing of leaf blades and leaf tips.
· Some wheat varieties may exhibit a reddening or purpling of the of the flag leaf.
· Early symptoms of aster yellows may resemble those associated with Barley yellow dwarf virus.
Diagnosis:
Nested polymerase chain reactions (PCRs) provide rapid diagnosis with great accuracy. Previous identification methods included DAPI staining, Dienes’ staining, dodder transmission to a susceptible host such as periwinkle, and transmission electron microscopy. Immunological methods such as ELISA are not widely available.
Problem:
Affected plants produce sterile heads with distorted awns or fail to produce heads.
Applications of insecticides are not recommended because the leafhopper vector is very mobile and omnipresent in crop production fields
Categories: Small grains, Diseases, Aster yellows
Date: 08/02/07