The corn smut fungus (Ustilago maydis) is either a disease or a delicacy, depending on where you live or whom you ask. Gardeners anticipating perfect sweet corn ears find the greenish white galls filled with black spores disagreeable, if not downright disgusting.
On the other hand, fans of authentic Mexican food greet the fungus (known as huitlacoche in Mexico) as a rare treat that adds a smoky, mushroom flavor to quesadillas, tamales, soups, and other Mexican dishes. Huitlacoche ("wee-tlah-KOH-cheh"), also referred to as Mexican corn truffle, can be eaten either cooked or fresh.
Spores of this fungus overwinter in infected plant debris and the soil. Wind and manure from animals that have eaten infected corn can also introduce the spores into the garden.
The fungus infects the plant through wounds caused by cultivation, hail, or insects. It can also infect newly formed silks. Galls are usually larger and more obvious on the ears, but you may also find them on the leaves, stalk, tassels, and aerial roots.
Higher rates of infection occur during years with warm, dry early summers followed by rainy weather. Soils high in nitrogen or manure also seem to increase the risk of disease, potentially because high nitrogen levels produce succulent, disease-prone foliage.
If you wish to control the fungus, remove any galls before the dark spores form inside. Burn or bag and throw away the diseased plant parts to prevent spreading the disease.
Many sweet corn varieties, including 'Silver Queen and 'Golden Beauty', are very susceptible to the fungus. Rotating your corn crops and planting sweet corn varieties with a built-in resistance to the disease, such as 'Silver King', 'Seneca Sensation', and 'Fantasia', can help control the problem.
Also, remember that huitlacoche is intentionally cultivated in Mexico, where this pricey treat is sold in fresh, frozen, and canned forms. So why not live on the wild side and add some huitlacoche to a breakfast burrito, taco, or tamale?