MANHATTAN, Kan. – Rain before and after flowering in some wheat this year led to head scab in parts of eastern and central Kansas, a Kansas State University plant pathologist said.

If wheat is infected with head scab, producers may need to handle the grain differently, depending on the level of infection, said Erick DeWolf, with K-State Research and Extension.

“It is important to scout fields now to know which fields have the most damage,” DeWolf said. “The disease incidence can be determined by simply counting the number of infected heads in five groups of 20 heads (100 total). The number of infected heads will give you a good estimate of the disease incidence. Fields with less than 2 percent incidence should not have significant yield losses, however, the likelihood of yield losses increases when incidence is greater than 10 percent.”

The diseased grain may have a reduced test weight and some of the kernels will likely be light colored, he added. 

At harvest, growers should check the quality of the grain periodically. Although combines are not great at separating the grain by kernel density, it may be possible to remove some of the most heavily damaged grain by slightly turning up the air speed on the combine. Severely damaged grain may be subject to price discounts upon delivery and the most severely damaged loads may also be rejected, DeWolf said.

At the elevator, grain inspectors will look for scab-infected kernels and treat them the same as any other kind of damaged kernel, said Randy McCormick, manager of the Kansas Grain Inspection Service, Inc. (KGIS). Wheat can have up to 2 percent damaged kernels and still grade No. 1; up to 4 percent to grade No. 2; and up to 6 percent to grade No. 3.

“Beyond that, however, elevators and other grain buyers may choose to have the wheat tested for DON (vomitoxin) levels,” McCormick said. It is not a requirement, but the KGIS can perform the test at the elevator if requested. Flour mills are often concerned about high DON levels in wheat.

Producers should begin developing a plan now to deal with the diseased grain, and it might be wise to dedicate a portion of the on-farm storage or equipment shed just in case a load of grain is rejected and needs to be handled separately in the middle of harvest, DeWolf said.

“It may still be possible to use this damaged grain as part of a cattle ration, or clean the grain to improve the test weight using seed cleaning equipment. Nothing is more frustrating than losing time during the grain harvest, and a little preparation may help you make good marketing decisions,” DeWolf said.

If the grain will be used for seed, plan to clean the grain heavily to remove the damaged kernels, said Vernon Schaffer, K-State Foundation Seed manager. Commercial seed cleaning equipment should be able to remove most of the diseased kernels, because they are smaller and lighter weight than the healthy kernels, he said.

“The first level of cleaning for scabby wheat should be screening and aspiration,” Schaffer said. “This primary cleaning method can take out much of the lighter-weight, scabby kernels, depending on the level of cleaning desired. The limitation of this method is that quite a bit of non-scabby wheat may also be removed, resulting in high cleanout rates in some cases.”

Another option is to have the grain cleaned with a gravity table, said Daryl Strouts, executive secretary of the Kansas Crop Improvement Association.

Fewer seed cleaning operations have this equipment, but it can be efficient at removing light-weight kernels. A gravity table will take out low-test-weight wheat with relatively low cleanout.

After cleaning to increase the test weight to at least 56 pounds per bushel, and germination to at least 80 to 90 percent, the grain can be used as seed if desired, Schaffer said.    This seed should be treated with a fungicide seed treatment, however, since the scab fungus can also cause seedling blight the following growing season, added DeWolf.

Scabby wheat, or even the cleanout from scabby wheat, also can be used as livestock feed, he added.

The relative feed value of scabby wheat is often very good, according to the K-State Department of Plant Pathology Fact Sheet titled “Wheat Scab.” However, scabby wheat may contain the mycotoxins DON (vomitoxin) and zearalenone.

“Neither of these toxins is considered carcinogenic or highly toxic, but they both can reduce the performance of livestock. Wheat should only be a small portion of the total feed ration and use caution when feeding animals severely damaged wheat,” according to the fact sheet.

Testing for DON is available through the Comparative Toxicology Lab, College of Veterinary Medicine, Kansas State University, Manhattan, KS 66506. The telephone number for the lab is (785) 532-5679. The lab can make recommendations for the appropriate dilution of feed which has high toxin levels.

Producers can also ask the lab about the availability of an inexpensive strip test, which can be used to give a quick indication of whether DON is present in a sample. This test will not measure exact amounts of DON, but will let a producer know whether there is a potential problem that might require further testing. The strip test can be purchased from the lab.

More information is available on the Department of Plant Pathology Fact Sheet titled “Wheat Scab” on the Web. Access http://www.plantpath.ksu.edu/ and search for Wheat Scab. 

-30-

K-State Research and Extension is a short name for the Kansas State University Agricultural Experiment Station and Cooperative Extension Service, a program designed to generate and distribute useful knowledge for the well-being of Kansans. Supported by county, state, federal and private funds, the program has county Extension offices, experiment fields, area Extension offices and regional research centers statewide. Its headquarters is on the K-State campus, Manhattan.

Story by: Steve Watson
swatson@ksu.edu
K-State Research & Extension News

Erick DeWolf is at 785-532-3968 or dewolf1@ksu.edu; Vernon Schaffer is at 785-532-6115 or vas@ksu.edu