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Ustilago maydis a1 (2)

by Jerzy Opioła. CC BY-SA 4.0

A close up of a plant infected with Ustilaginales smut
Often a disease that affects cereal crops and many other members of the grass family but can be an issue in gardens. It is difficult to treat once infected as the spores can stay dormant for up to 7 years in the soil waiting for a host and the right conditions.
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Depending on species: Some cause small yellow spots on leaves. Some completely distort and stunt the plant's growth. Many causes swelling of certain tissues that when opened are shown to be filled with brown-black spores.

Growth factors

Having wounds in a plant. Hot and dry weather


Yellow spots on leaves.
Seed distortion or swelling.
Poor growth.

Biological treatment

Removing and burning infected parts of the plants can interrupt the fungi's lifecycle.

Chemical treatment

Chemical treatments are ineffectual due to the longevity of the spores in the soil.


The spores germinate in the spring and infect young plants through wounds. The fungi multiply inside areas of plants causing them to swell. These swellings will eventually dry out and burst open releasing massive amounts of black spores that infect other hosts.


Keeping good hygiene around plants eg removing fallen leaves, removing and burning infected materials etc. Not growing on a site that has had a smut infection previously. Making sure that plants do not become too dry in hot weather. Keeping good air circulation around and through plants. Keep damage to plants a minimum to reduce infection points.

Affected plants


Zea mays

A close up of a blue Anemone apennina flower

Apennine Anemone

Anemone apennina

A close up of a flower garden with some orange Calendula officinalis flowers


Calendula officinalis

Border Carnation 'Odessa'

Dianthus 'Odessa'

Garden Dahlias

Dahlia spp.


Allium spp.

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