The virus is transmitted by thrips. No control is known. Aster yellows is caused by a mycoplasma and is transmitted by leafhoppers. Plants are light yellow in color and stunted. Petioles become curled, twisted and brittle.
Leaves become thickened and brittle.
Blackheart is characterized by death of heart leaves which turn black. Softrotting bacteria frequently invade necrotic tissue, causing watery rot. It is a complex physiological disease, but deficiency of calcium in the growing tip is associated with disease. High temperatures, rapid growth, and lack of water are often associated with the disease, and excessive soil salinity and nitrogen are also believed to favor it. Timely irrigations to prevent stress of the plants helps to prevent blackheart.