Certain pre-plant nematicides can be used where the soil is infested. Infected seedlings wilt, turn brown and die, resulting in poor stands. Plant on a bed, do not overwater, and control weeds as soon as possible after emergence. The first symptom of aster yellows is yellowing of the foliage, followed by excessive growth and bunching of shoots. Older leaves become twisted and may fall off.
Roots are misshapen, and of poor quality with many adventitious roots.
The organism is introduced in the field by leafhoppers from overwintering infected weeds. The disease usually occurs sporadically with little economic loss. Symptoms begin as small, yellowish spots on both sides of the foliage. Spots enlarge quickly changing from yellow to ash-gray with the tissue drying in affected areas. The fungus also attacks leaf petioles and stems.