What is in this article?:
- New stripe rust race breaks resistance
- Fungicide trials
- New stripe rust race
- Breaking down variety resistance
- Integrated approach is key
The test included multiple fungicide applications including an untreated check, single and multiple applications beginning at flag leaf emergence and continuing until the head fully emerged. Fungicide applications consisted of 10.5 ounces per acre of Quilt (active ingredient Azoxystrolin and Propiconazole) with a 0.25 percent nonionic surfactant.
“We recorded severity ratings on a weekly basis following the first application,” Duncan said. “Ratings and yield data indicate varietal resistance in Fannin was enough to manage the new race of stripe rust. However, susceptible varieties such as TAM 112 required at least one fungicide application to manage the disease.”
He said TAM 304 showed “tolerance but not resistance,” to the new stripe rust race. TAM 112, a susceptible variety, produced 55 bushels per acre with a fungicide treatment but only 32.4 bushels untreated.
Fannin, untreated, averaged 57 bushels per acre. With a single application, yield was 58 bushels per acre and with two applications was 58.3 bushels per acre. “We see no significant difference in yield. It is a waste of money to spray fungicide on Fannin for stripe rust control,” Duncan said.
With susceptible varieties, timing makes a difference, he said. “Protecting the flag leaf might seem to be equal to a double fungicide application,” Duncan said. “But that’s not always the case.”
He said growers also have to consider whether applying a fungicide to a susceptible variety has “a significant effect or is an economical treatment. Knowing the disease resistant traits of each variety is a key to managing disease economically.”
Treatment costs range from about $10 per acre for generic fungicides to $18 for brand name products.
Duncan said a new variety, TAM 113, which will be available this year, is resistant to both stripe and leaf rust. It’s adaptable to the High Plains and is comparable to TAM 111. He said TAM 304 is a good option for Central Texas.