Key Features
- Leaf and vein yellowing
- Stunted and deformed flowers
- Bushy, overproduction of stems
Symptoms
Aster yellows is caused by a small, bacteria-like organism known as a phytoplasma. Symptoms include leaf and vein yellowing, stunting, deformation of floral structures, and abnormal multiplication of stems resulting in bushy growth. Examples of deformation include, but are not limited to, green flowers, leaves or shoots growing from floral structures, or even multiple flowers growing from the center of an infected flower. Severe infections can kill the host, which fails to overwinter, and return the following spring. Symptoms first appear in mid to late spring after leafhoppers appear.
Biology
The aster yellows phytoplasma survives in perennial hosts, including weeds. Aster leafhoppers are capable of carrying the pathogen north from southern states and transmitting it to healthy plants as they feed. Leafhoppers are the only known means by which aster yellows moves between plants. Symptom development is much more pronounced in hot weather.
Management Recommendations
There are no treatments available for aster yellows. Remove weeds and infected plants to reduce additional infections within the landscape. Aster leafhoppers feed on a wide spectrum of plants, but prefer those in the Aster family. Decreasing the number of susceptible plants and incorporating non-host species into the planting will reduce aster leafhopper numbers. Managing leafhopper populations with insecticides is not a reliable control method.
Effective Pesticides
Pesticides are neither available nor recommended for managing this disease.
Resources
- Aster Yellows
- Not satisfied with ID? Contact the Purdue Plant and Pest Diagnostic Lab
- Sign Up for the Purdue Landscape Report
