Some Kansas wheat producers are reporting above normal levels of head scab in their crops, according to a Kansas State University scientist.
"Head scab was favored by frequent rainfall that occurred just prior to and during the time of flowering," said Erick DeWolf, K-State Research and Extension plant pathologist."
"The disease is most common in the eastern third of the state, but can also be found at low levels in parts of central Kansas," DeWolf said. "The symptoms of head scab include large tan or white lesions that encompass one or more spikelets. Heads infected by scab will often have a brown discoloration of the rachis (central stem of the wheat head) and the developing kernels will have a white chalky appearance. The base of diseased spikelets may also have a small pink mass that is produced by the fungus that causes head scab."
Nothing can be done at this point to prevent head scab, although it is important for producers to be scouting their fields for the disease, he said. The symptoms become most obvious as the wheat moves into late milk and early dough stages of development.
"It will be important to check multiple times during the grain filling period because the symptoms of head scab can change rapidly in just a few days," DeWolf said. "It is common to see the incidence of scab symptoms increase dramatically in a three- to five-day period."
The infection typically takes place during flowering and the early stages of grain fill, and would require fungicide applications of products such as Folicur, Proline, or Caramba (all newly labeled products) to suppress the disease. Producers should also avoid using the most susceptible varieties and avoid planting wheat after corn, which is also a host of the fungus, DeWolf said.
Cropping systems and tillage systems have an effect on the development of head scab in wheat, said Jim Shroyer, K-State Research and Extension crop production specialist. Corn residue and infected wheat residue are prime sources of head scab infections in the spring near flowering time, he said.
Wheat planted into or near corn residue, or continuous wheat planted into fields with infected wheat residue or infected wheat seed, is often more likely to have head scab infections than wheat planted after a broadleaf crop, grain sorghum, or on fallow ground, DeWolf said. However, wheat planted after a broadleaf crop or grain sorghum may still get infected with head scab some years since the Fusarium fungus is airborne and may travel great distances from the original source of inoculum -- corn, wheat, or grass residues.
Broadleaf crops such as soybeans, sunflowers, canola, and cotton are not hosts of the Fusarium head scab fungus, said DeWolf.
Where scab has been a problem, producers may want to rotate to one of those crops the following year, added Shroyer.
Producers who irrigate wheat should avoid watering the wheat during flowering through early grain fill, said Shroyer.
More information on head scab in wheat is available on the Department of Plant Pathology Fact Sheet on the Web at: http://www.plantpath.ksu.edu/ and type in Wheat Scab.