Chrysanthemum white rust

Leaves
Following infection, pale-green to yellow spots, up to 5 mm in diameter, develop on the upper surface. The centres of these spots become brown and necrotic with aging. On the corresponding lower surface, raised, buff or pinkish, waxy pustules (telia) are found. As the spots on the upper surface become sunken, so these pustules become quite prominent and turn whitish when basidiospores are produced. Telia are occasionally found on the upper leaf surface. Severely attacked leaves wilt, hang down the stem and gradually dry up completely.

Bracts and stems
Sori sometimes develop when crops are excessively affected.

Flowers
Infection has been recorded as necrotic flecking with occasional pustules.

Control
Preventive spraying with fungicides is effective but costly. Active ingredients found useful include oxycarboxin, triforine, benodanil, triadimefon, diclobutrazol, dibitertanol and propiconazole. Some chrysanthemum cultivars are resistant and breeding for resistance continues.