Geraldton waxflower (Chamelaucium uncinatum Schauer, family Myrtaceae), indigenous to western Australia, is cultivated commercially in South Africa as a cut-flower crop and exported to markets in the Northern Hemisphere. In September 2000, disease symptoms were observed on 4-year-old plants in a commercial orchard of C. uncinatum cv. Ofir in Philippe, in the Western Cape Province. The base of the petals and the calyxes of the waxflowers showed brown necrotic lesions. Eventually the calyx and all the petals turned brown, and the flowers shriveled and abscised. B. cinerea Pers.:Fr was consistently isolated from affected petal and calyx tissues. When placed in a moist chamber, conidia and mycelia formed on the surface of dead and infected tissue. Koch's postulates were confirmed by spraying flower stems of C. uncinatum cv. Ofir with a spore suspension (1 × 106 conidia per ml). Inoculated flower stems were placed in a bottle filled with water and enclosed in transparent plastic bags for 24 h at 21°C. Typical symptoms developed on the petals and calyx within 3 days after inoculation. B. cinerea was reisolated from affected tissues. Botrytis flower blight or gray mold, causing a flower petal disease, has been recorded on C. uncinatum in Australia (1), but this is the first record of Botrytis flower blight of C. uncinatum in South Africa. Because Geraldton waxflower is a major cut-flower crop grown for export, this disease can cause significant losses to the industry, especially under cool, wet growing conditions.
Reference: (1) A. Tomas et al. Aust. Plant Pathol. 24:26, 1995.
