Environment

White spores on the underside of mist flower leaves.
Source: Landcare Research Biocontrol agent:
Mist flower fungus

Scientific name:
Entyloma ageratinae

Target weed:
Mist flower
Ageratina riparia

What does mist flower fungus look like?

White spores germinate in spring and infection continues in favourable conditions of warmth and high humidity. The host plants develop reddish-brown lesions with yellow margins on the upper surface of the leaves. The underside of each lesion has matching white spores giving a powdery white appearance. These characteristic white spores give rise to the common name, ‘white smut’.

The spores are spread mainly by wind, but also by rain and splashing water over smaller distances. As the disease progresses, the lesions on the upper surfaces coalesce and become dark brown.

What could it be confused with?

There is another fungus (Phoma) that causes similar disease symptoms on mist flower in New Zealand, except that it does not produce white spores. Unless the characteristic white spores of the white smut fungus are present, only an experienced plant pathologist will be able to tell symptoms caused by the two fungi apart.

Where is it found?

It is widespread throughout Northland

When and how is it best harvested for redistribution?

Collect infected leaves in spring when conditions are most favourable, by looking for white spores on the undersides of the leaves. Drag a bundle of infected leaves through wet mistflower at clean sites to distribute spores or wipe infected leaves with a damp cloth and wipe on uninfected plants.