Mosaic (virus - TMV): Crinkled leaves with yellow and green areas. Plant may be stunted. Destroy diseased plants. No control.
Crown Rot (fungus - Phytophthora parasitica): A black discoloration and dry rot of the crown and lateral branches occurs near the soil line. This is followed by wilting and death of the affected plants.
Aster Yellows (mycoplasma): Plants are yellowish, bushy, and dwarfed with many rosette-like, secondary shoots. Flowers often malformed and greenish. Leaves may curl, turn yellow or purple.
Root Knot (nematode - Meloidogyne spp.): See section on Root Knot.