Beth Ellen Doran, Iowa Master Gardener and Beef Specialist
Most fellow gardeners said 2022 was a hard year to garden. The year started off dry and cool and continued dry, except with heat and wind. This made for tough growing conditions, and my ornamental corn is proof of this.
I started with high hopes of producing about a dozen colorful ears for fall decorations, but mother nature didn’t quite cooperate. In August, I spied an ear with white growths (galls) which an Extension specialist diagnosed as common smut. The causal agent is the fungus Ustilago maydis.
Galls are abnormal fungal growths that can appear anytime throughout the growing season. They are especially active in young growing tissue (ears, leaves, stalks, and tassels). The galls initially appear as white- to silver-growths, but later turn black as fungal spores develop inside the galls.
What conditions favor common smut? It is usually most severe when young tissue is wounded by hail, wind, or insects. The fungus typically infects corn ears via the silks when there are poor pollination conditions. Infection is favored by warm weather (79-93° F) and moderate rainfall. Hot, windy weather prevailed when my corn was pollinating.
Once galls have formed, there is no treatment. They should be removed and destroyed by burning or burying before they burst to prevent the spores from spreading and overwintering. Fungicides are ineffective in controlling common smut. The disease is best managed by planting a resistant variety, avoiding plant injury, and rotating the garden crops.
Luckily only one ear had common smut, but heat stress affected the other ears. Heat stress during silking and pollination can interfere with successful pollination and reduce photosynthesis. Both may increase kernel abortion on the tip of the ear (called “tip back”) and a reduction in the number of kernels on the ear. However, heat stress can also reduce kernel size.
At any rate – whether my ornamental corn is perfect or not, I will chalk 2022 up to experience. I disposed of the infected ear and plan to decorate with the “normal” ears. And for those that are not perfect, I’m sure the squirrels will enjoy feasting on them! Common Smut;
Photo by Doran Beth Ellen Doran, Iowa Master Gardener and Beef Specialist Iowa State University Extension and Outreach 712-737-4230 or doranb@iastate.edu