The Q&A Archives: Smut Disease on Corn

Question: Several years ago my corn developed big, black, greasy-looking growths on the ears, which I was told was the fungal disease corn smut. I have no idea where it came from, although I do live in a very rural area with much acreage in silage corn. I carefully removed the smut-covered ears, placed them in a plastic bag and discarded them without disturbing the spores. But despite this care, every year it returns. I have even moved the corn patch to a different area of the yard. Can you recommend a way of ridding myself of this fungus?

Answer: Corn smut is caused by the fungus Ustilago zeae. The fungal spores can remain in the soil 2 or 3 years, and spores can be wind-blown long distances. Infection occurs in the seedling stage at soil temperatures of 70F to 86F degrees.

The best ways to control this problem is to stop planting corn for 3 or 4 years in lightly infested fields, or try planting resistant varieties. Another method to "outwit" the fungus is to plant your corn seed shallowly to promote rapid germination, or try pre-germinating your seed by placing between two damp paper towels. If you can keep the seedbed moist the first 4 weeks after planting, you may be able to discourage fungal growth.

Some studies have shown that a "living mulch" of white clover sown between the corn rows can help suppress the corn smut fungus. However, note that you may need to water the planting more often, as the clover will compete with the corn for water.

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