Damage Pattern
The first symptoms of maize smut can appear as early as the 4-5 leaf stage. On the main veins of the leaves, small dents or bulges form, which initially have a silver-gray skin and later dry out. Stronger spherical leaf deformations may also occur, often on leaves that have been previously damaged by frit fly larvae. The infestation is primarily on injured, rapidly growing tissue. As the plant continues to grow, dents can form on newly developed organs, particularly the flag leaves and the cob. Cob formation can be negatively affected, resulting in grain transformation into scorched marks. In later stages of vegetation, other fruiting bodies may develop below the cob, for example, in the axillary buds. Yield losses depend on the location and severity of the infestation. The fungus is not toxic and is considered a delicacy in parts of South America under the name "Huitlacoche."
Biology
The growths release black-brown spores that are initially greasy and moist but later turn powdery. These spores can survive in the soil for 6-10 years. The primary infection starts in spring from the soil, where spores germinate with sufficient moisture and higher temperatures. The pathogen enters the plant through stomata or wounds, leading to pathological multiplication and cell enlargement. Injury caused by pests, growth cracks, drought stress, heat, and late frosts increases the plant's susceptibility to infection.
Control
Direct control of maize smut is not possible. However, control of frit fly larvae and European corn borer, which create entry points for the fungus through their leaf feeding, can reduce the risk of infestation. Additionally, choosing varieties with lower susceptibility to the disease and avoiding late sowing can also help reduce the risk.