Confirmation of ray blight disease of pyrethrum in Australia

Isolations from affected plant parts of pyrethrum exhibiting flower bud abortion and necrotic symptoms consistently yielded a Phoma sp., identified as the anamorph of Didymella ligulicola, the causal agent of ray blight of chrysanthemum. Pathogenicity of both mycelial and conidial inoculum of the isolated fungus to pyrethrum was proven. Infection of stem pieces occurred by direct penetration of the fungal hyphae with invasion being both inter- and intracellular. Infection was associated with red pigmentation and cytoplasmic crystalline inclusions of host tissues. This is the first confirmed record of this disease of pyrethrum in Australia.