This is common corn smut, Ustilago maydis, a fungus. Some corn varieties are susceptible, other varieties are tolerant or resistant. Spores germinate on corn plant surfaces, particularly in wounds that could result from hail damage or corn stalks rubbing against each other in winds. The smut mass grows, forming a tumor-like gall, sometimes to about fist- sized. Then the outer silvery-white membrane ruptures to release thousands of brown-black spores, much like a “puffball”. Several Latin and Oriental cultures consider the developing smut mass (before it ruptures to release spores) a delicacy stir-fried or cooked. This infection thrives with dry soils early in the season followed by rainy periods and 80-95 degree temperatures. Unless you plan to eat smut masses, cut them out of the tassels, remove infected ears, or prune out the infected stem before masses rupture. Bag these and discard with the trash. Note which corn varieties seem particularly susceptible and avoid planting them in future years.

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