In this issue:
| Vol 4 No. 7 | August 23, 2002 |
Corn Smut Hits Again: Cause and Cure?
Dr. Vince Fritz, Extension Horticulturist, Southern Research and Outreach Center, University of Minnesota, Waseca
 Photo courtesy of Dr. R.C. Rowe, Ohio State University |
Corn smut has once again raised its spores and angst in some sweet corn fields in southern Minnesota. There are many theories and remedies for this unpredictable pest. Here I provide an overview of the problem and suggestions for control. Smut spores overwinter in galls and plant parts on the soil surface. They can spread by running water, machinery, insects, and mostly by wind. Once germination of spores begins, a second crop can be produced from the germinated spores as rapidly as 4-6 hours later. Optimum temperature for development is about 86 F. All tender and succulent aerial parts of the plant are susceptible to infection. Most infections occur at the leaf whorl stage and gain entry through the leaf whorl. Infection of the fungus is direct and does not require entry through stomates or other injury entry points on the corn plant. |
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There is no general consensus on weather conditions that most favor disease development. However, rainfall and humid conditions usually are the most critical factors affecting infection. Moisture is needed for spore germination, however water on the leaves is not essential once the plant is infected. Contrary to many people’s views, corn smut is less prevalent when the corn crop has been growing at a steady and normal rate. Continued and rapid development of corn plants appears to give the plants some degree of resistance or ability to escape infection. A sudden increase in smut presence can sometimes be related to plant injury that may have occurred within 2 weeks before tasseling; this is usually caused by hailstorms. To my knowledge, there isn't any consistent relationship between amount of injury and disease severity.
Strategies to control the disease such as crop rotation are only marginally successful because of the mobility of wind blown spores. Currently the most successful means of control is the use of resistant varieties, removal of smut galls, and sometimes a targeted use of fungicides into the whorl.
For more information, see the Corn Smut Fact Sheet (Ohio State University) is on the web at: http://ohioline.osu.edu/ac-fact/0016.html
Co-Editors: Bill Hutchison, Department of Entomology,
University of Minnesota, hutch002@tc.umn.edu
Jeanne Ciborowski, IPM Program, Minnesota Department of Agriculture,
jeanne.ciborowski@state.mn.us
Cindy Tong, Department of Horticulture, University of Minnesota,
ctong@extension.umn.edu
Production Editor: Suzanne Wold, Research Assistant, University of
Minnesota, woldx018@tc.umn.edu
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Last Revised August 23, 2002.
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