A Texas AgriLife Extension Service state small grains specialist advises wheat producers to use an integrated approach to managing new instances of stripe rust.
"Last year a new race of stripe rust moved into Texas, infecting wheat varieties that were previously resistant, such as Jagger and Jagalene," said Dr. Robert Duncan, AgriLife Extension small grains specialist. "Only three varieties remain resistant, including TAM 111, Fannin and Doans. With a limited number of highly resistant wheat varieties, producers will need to use an integrated approach to managing this disease."
Duncan presented his latest research at the American Society for Agronomy/Crop Science Society of America/Soil Science Society of America International Meeting in Long Beach, Calif. Nov. 1.
Duncan said a trial was conducted this past season to determine how resistant, intermediate and susceptible varieties "interact with one or multiple fungicide applications.”
"Confirming previous results, when a susceptible variety is under severe rust pressure, a fungicide application can have a significant impact on yield," Duncan said.
For example, a susceptible variety like TAM 112 only yielded 32 bushels to the acre when left untreated under severe stripe rust pressure, Duncan said. When TAM 112 was protected with multiple fungicide applications, the yield doubled to 64 bushels to the acre.
On the other hand, a resistant variety like Fannin did not experience a difference in yield between the untreated (57 bushels to the acre), a single (58 bushels to the acre), a double (58 bushels to the acre) or a quadruple fungicide application (58 bushels to the acre), Duncan said.
"This demonstrates the need for understanding the characteristics of the varieties you may be growing, and proves that management decisions for each variety need to be made individually."
Duncan explained that a single fungicide application at Feekes 8.0 (flag leaf stage) was statistically equal to a double application at Feekes 9 and 10 (ligule of flag leaf visible and boot stage) for all varieties tested. "This proves how critical the application timing can be."
For more information on small grains production in Texas, visit http://varietytesting.tamu.edu/wheat.