Ohio State University Extension Bulletin

Wheat Disease Management in Ohio

Bulletin 785

Crop Rotation

In the humid Midwestern United States, wheat should never follow wheat or spelt in the rotation sequence. Severe soilborne diseases, like take-all (Figure 9) and Cephalosporium stripe (Figure 10), can cause complete crop failure in continuous wheat systems. Foliar diseases, like powdery mildew, tan spot, and the Stagonospora diseases, can also be quite severe in fields with no rotation. In years with mild winters, the leaf rust fungus may survive and cause early leaf infections that initiate the epidemic within the immediate area.

Crop rotation of two years away from wheat is usually sufficient to eliminate most disease problems. Crop rotation controls disease by providing sufficient time between susceptible crops for the disease organism (fungi or bacteria) to die out. When the population of the disease organism is reduced to such low levels that the disease is unlikely, then wheat can be grown in the field again. Most crops (corn, soybean, alfalfa and other hay crops, oats, barley, sugar beets, potatoes, and vegetable crops) are suitable for the rotation. However, there are exceptions. Wheat planted into corn residue is more likely to have head scab (Figures 11, 12, and 13). The wheat scab fungus is the same pathogen that causes Gibberella stalk rot of corn.

Figure 9. Take-all is a serious disease whenever wheat is grown continuously or in fields with persistent perennial grass weed problems. Take-all attacks the roots of the plant, causing a black scurfy appearance on roots and lower stems. It is usually first recognized when plants die prematurely in patches. Figure 10. Cephalosporium stripe is another soilborne disease that occurs in wheat fields planted after wheat or grass sod or in fields with a perennial grass weed problem. Yellow stripes that extend from the leaf tip to its base are characteristic for the disease.

Figure 11. Fusarium head scab is common in Ohio wheat fields when rain persists through the flowering period of the crop. Florets in affected heads are killed, bleached white, and develop salmon-pink spore masses on the edges of their glumes. Kernels in infected florets are shriveled, whitish to pinkish in color, and have poor germination. Figure 12. Heads of wheat with different proportions of spikelets affected with Fusarium head scab.

Figure 13. Fusarium head scab — shriveled, moldy seed from diseased head.

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	Figure 9. Take-all is a serious disease whenever wheat is grown continuously or in fields with persistent perennial grass weed problems. Take-all attacks the roots of the plant, causing a black scurfy appearance on roots and lower stems. It is usually first recognized when plants die prematurely in patches.		Figure 10. Cephalosporium stripe is another soilborne disease that occurs in wheat fields planted after wheat or grass sod or in fields with a perennial grass weed problem. Yellow stripes that extend from the leaf tip to its base are characteristic for the disease.
	Figure 11. Fusarium head scab is common in Ohio wheat fields when rain persists through the flowering period of the crop. Florets in affected heads are killed, bleached white, and develop salmon-pink spore masses on the edges of their glumes. Kernels in infected florets are shriveled, whitish to pinkish in color, and have poor germination.		Figure 12. Heads of wheat with different proportions of spikelets affected with Fusarium head scab.
			Figure 13. Fusarium head scab — shriveled, moldy seed from diseased head.