Bud rot causes numerous spots on unfolding leaves. The spots run together along veins. The spots may be whitish at first but soon turn black. Infected flower buds turn black and die before opening. The disease moves down the leaf stalk, killing young stems and buds. On older leaves, the disease spreads slowly, forming irregular, yellowish spots with water-soaked margins. Use only healthy roots. No chemical control is listed.
Canna mosaic virus causes leaves to have pale yellow stripes from the midrib to the margin. The leaves are wrinkled, curled, chlorotic and are often dusty brown. The stems, sepals and petals have yellow bands. Destroy infected plants and control the aphids which spread the disease. No chemical control is listed.
Aster yellows causes irregular, diffuse, dull yellowing of young leaves which turn brown with age. Infected plants are destroyed. The disease is spread by aphids. No chemical control is listed.