Common Smut

Common smut forms galls that start small and pale but can grow considerably larger than the tissue they replace, developing a shiny, greyish-white membrane. As galls mature internally, the membrane darkens and eventually ruptures, releasing a mass of powdery black spores.

Teliospores surviving in soil or crop residue germinate under suitable conditions to produce infective structures that penetrate young, actively growing maize tissue, most often through wounds. Common wounding sources include hail damage, insect feeding, wind-whipped leaves, and mechanical injury from cultivation.

Soil- and residue-borne teliospores

Persist for a number of years, providing inoculum for future maize crops on the same land

Wound-dependent infection

Meristematic tissue exposed by hail, insects, or mechanical damage is particularly susceptible

Local gall development

Infection typically produces localised galls rather than a systemic, whole-plant disease

Maize is the primary agricultural host of Ustilago maydis. The fungus is highly adapted to this host, and disease pressure is closely tied to the frequency of maize in a field's cropping history and to local conditions that create wounding opportunities.

• Wounding events such as hail, insect feeding, or mechanical damage during the growing season
• Excess nitrogen supply promoting succulent, more susceptible tissue
• Frequent maize in the rotation, building up soil and residue inoculum over time
• Warm temperatures with intermittent moisture during susceptible growth stages

Because infection depends heavily on wounding and on soil-borne inoculum, prevention focuses on reducing plant injury, managing nitrogen, and lowering inoculum load through rotation.

• Choose resistant or tolerant hybrids where available
• Rotate away from maize to reduce soil and residue inoculum over time
• Avoid excessive nitrogen applications that promote succulent, susceptible tissue
• Where practical, remove and destroy galls before they rupture to limit local spore release