The center leaves fail to develop normally and remain as short, thickened stubs in the middle of the head.
Outer leaves become yellow and twisted.
Pink to tan latex deposits collect on the underside of midribs of affected leaves. If young plants are infected, outer leaves yellow and the plants may be severely stunted. If older plants are infected, latex spots in the interior of the head may be the only symptoms. The principal vector is the aster leafhopper, Macrosteles quadrilineatus, although the phytoplasma can be transmitted by many other species of leafhoppers. Leafhoppers can remain inoculative for at least 100 days.