Corn smut

Corn Smut

File:Corn smut on corn.jpg

Corn smut on an ear of corn

Corn smut is a plant disease caused by the pathogenic fungus Ustilago maydis. This fungus infects maize (corn) and is known for causing large, tumor-like galls on the ears, leaves, and stalks of the plant. These galls are filled with dark, powdery spores that are the reproductive structures of the fungus.

Biology of Ustilago maydis

Ustilago maydis is a basidiomycete fungus that primarily infects Zea mays, the common corn plant. The life cycle of U. maydis involves both asexual and sexual reproduction. The fungus produces teliospores, which are the overwintering stage, and these spores can survive in the soil for several years. When conditions are favorable, the teliospores germinate to produce basidiospores, which can infect young corn plants.

The infection process begins when the basidiospores land on the surface of a corn plant. The spores germinate and penetrate the plant tissue, leading to the formation of galls. These galls can appear on any above-ground part of the plant, but they are most commonly found on the ears and tassels.

Symptoms and Identification

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Close-up of a corn smut gall

The most distinctive symptom of corn smut is the formation of galls, which can vary in size from a few millimeters to several centimeters in diameter. Initially, the galls are covered with a silvery-white membrane, but as they mature, this membrane ruptures to release the black, powdery spores.

Infected plants may exhibit stunted growth, and the quality and yield of the corn can be significantly reduced. The presence of corn smut is usually easy to identify due to the characteristic appearance of the galls.

Economic Impact

Corn smut is considered a pest in many regions where corn is grown, as it can lead to significant yield losses. However, in some cultures, particularly in Mexico, corn smut is considered a delicacy known as "huitlacoche". It is used in various traditional dishes and is valued for its unique flavor and nutritional content.

Management and Control

Managing corn smut involves a combination of cultural practices and, in some cases, chemical treatments. Crop rotation and the use of resistant corn varieties can help reduce the incidence of the disease. Removing and destroying infected plant material can also help limit the spread of the fungus.

Fungicides are generally not effective against corn smut, as the fungus infects the plant systemically. Therefore, prevention through cultural practices is the most effective strategy.

Related Pages

• Maize
• Fungal plant diseases
• Huitlacoche