Stacy Campbell: Head scab wheat – harvesting and seed lot management
In last week’s article I wrote about a late season wheat disease that we typically do not see in the western half of the state called Fusarium Head Blight or more commonly known as head scab. The disease is rare in western Kansas, where dry conditions generally suppress disease development. However, this year has been the exception due to all of the precipitation we have received this spring, and it appears that numerous wheat fields have a low level of head scab.
I don’t think it is anything to get to worked up about but when harvesting, you may want to carefully watch your combines adjustment of air to try and remove or blow out more of the affected kernels that are typically shriveled and lighter. Another management tip is to harvest fields with the lowest disease levels first, which can prevent further degradation of grain quality. Where possible, avoid mixing healthy grain with loads of grain having higher disease levels.
The disease is easy to detect before the wheat turns in color, because head scab causes tan lesions that encompass portions of the wheat head. Infected spikelets are often brown at the base and can have orange fungal spores on the edges of the florets. Infections may damage the stem within the head, causing segments above the infection to die prematurely and turn white. The head symptoms are quickly masked by the maturation of the wheat crop; growers may not realize the full extent of the damage until harvest, when the Fusarium damaged kernels are visible in the grain. Diseased kernels are shriveled and have a white, chalky appearance. In some cases, the infected kernels may have a pink discoloration.
The next question on many farmers' minds is – can I keep this wheat back for seed wheat to plant this coming fall? As I had previously mentioned from the fields I have seen the head scab infection appears to be at low levels. The disease Fusarium graminearum also can cause seedling blight and root rot. If you do decide to keep back some of the infected seed for planting. Clean the seed rigorously, treat it with a fungicide, check the germination rate before planting and adjust the plant population appropriately. Seed lots with very low germination after cleaning should not be planted.
Fusarium growth production stop when grain moisture levels fall below 22 percent. Avoid storing seed lots with scabby kernels at high moisture levels, even briefly. Grain infested with Fusarium that has been cleaned to remove the lighter, scabby kernels will store better than infected grain that has not been cleaned.
The Kansas Crop Improvement Association in Manhattan does seed germination tests for a nominal fee of around $18 per sample. This year with the head scab it may well be worth the money to send your potential seed wheat off first for a germination test, especially before going to the expense of seed cleaning and a seed treatment. You can contact our offices in Hays or Great Bend for the form for the germination test. We would also be glad to send the sample(s) in for you or provide you with the mailing address and form.
If you wish to learn more about Fusarium Head Blight (head scab), go to www.cottonwood.ksu.edu click onto the Crops and Livestock tab and look under Hot Topics for Head Scab.
Stacy Campbell is an Agriculture and Natural Resources agent in the Cottonwood District (which includes Barton and Ellis counties) for K-State Research and Extension. You can contact him by e-mail at firstname.lastname@example.org or calling 785-628-9430.