Flag Smut in Wheat

Update on Flag Smut in Kansas

During the week of May 6, 2015, wheat flag smut (Urocystis tritici) was initially detected in a field demonstration plot in Rooks County and confirmed by laboratory result during regular and on-going disease survey work. 

Since that initial detection, additional survey teams were deployed to scout for the disease.  Kansas Department of Agriculture is working closely with K-State Plant Pathology, K-State Research and Extension and USDA APHIS PPQ to conduct additional surveillance.

KSU and KDA have jointly conducted field surveys since 1976.  It was during routine disease survey work that wheat flag smut was observed.  Flag smut spores can live in the soil and survive in wheat relative plant species allowing the disease to potentially maintain a low-level, undetected presence in the state.  Weather conditions during the growing season for this year’s wheat crop have been ideal for the spread of flag smut, particularly in the more arid regions of the state.

Flag smut presents no human or animal health concern and has no impact on grain quality.  It can have a negative impact on wheat yield, the severity of which is determined by the infestation level of the field. 

Kansas farmers are encouraged to be especially cognizant during wheat planting season to select wheat varieties with high resistance to fungal diseases as well as to apply fungicides to seed before drilling wheat this season. 

While the most effective way to break the disease cycle, which can lie dormant in the soil for as many as four or five years, is using fungicide treated seed, other recommended strategies include avoiding early planting conditions that place seed into warm moist soils, which are known to favor infection by the flag smut fungus and to consider crop rotation with non-host crops such as soybeans, sorghum and corn, to reduce the risk of the disease emergence. Continuous wheat often favors and creates ideal conditions for wheat diseases to flourish.

What is Flag Smut?

Flag smut (Urocystis tritici ) was first identified in arid regions of Australia in the late 1800s. It was known to be in Kansas in 1920-30s. A sizeable research plot in Leavenworth County by the Kansas State Research and Extension focused on smuts and bunts of small grain crops in Kansas. Following the establishment of the KDA/KSU plant pathology disease surveys in 1976, flag smut has not been seen in Kansas.

Flag smut is a fungus carried by spores that can be borne on the seed, blown by wind short distances or moved with machinery. The fungal spores produced near flowering of the crop have the possibility of surviving up to four years in the soil. The spores infect the seed prior to emergence from the soil. Symptoms include dark streaks on the leaves of the infected wheat plant and a twisted flag leaf. Flag smut tends to stunt growth and reduce tillering but has generally low impact on yield when compared with other wheat diseases.

Research has shown that the use of fungicide seed treatment, which is very economical, is highly effective in preventing the presence of flag smut and is important tool in successful mitigation of the disease.

There is no human or animal health concern or direct effect on grain quality related to flag smut.

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