March 17, 2015
shared from Texas A&M University’s AgriLife TODAY
Texas producers and AgriLife Extension specialists and agents have observed leaf and stripe rust throughout a large swath of the state from South Texas north into Oklahoma and in the San Angelo, Abilene and Chillicothe areas, said Dr. Clark Neely, AgriLife Extension small grains and oilseed specialist in College Station.
“Right now, stripe rust appears to be more prevalent than leaf rust, and in some cases, it has started to move into the upper canopy,” Neely said.
Stripe rust was first reported in Northeast Texas on Jan. 29, extremely early in the season, Neely said. In comparison, the earliest record of finding stripe rust was Jan. 8, 2005, which correlated with a severe epidemic of stripe rust across the Southern Great Plains. Another severe stripe rust epidemic occurred when stripe rust was observed on Feb. 20, 2010.
“Generally speaking, when stripe rust is observed before March, a large stripe rust epidemic is likely for the Southern Great Plains,” he said.
Neely said producers will need to take extra steps to protect against the disease, which left unchecked could result in as much as 70 percent reduction of yields in susceptible lines.
“Many growers have already applied an early fungicide application, which is not a typical practice, but likely warranted this spring with the high disease levels,” he said.
“This early fungicide application will not protect the crop for the rest of the season, and a second application will likely be needed after flag leaf emergence, assuming weather conditions remain favorable for the spread of the disease.”
Stripe rust development is most rapid between 50-64 degrees and favored by intermittent periods of rain or dew, similar to what is being experienced in of some areas of Texas, said Dr. Ron French, AgriLife Extension plant pathology specialist in Amarillo.
Strobilurin fungicides are best suited as a preventive control when applied before infection starts, while triazole fungicides typically have a better curative effect after infection is observed, French said.
Neely said leaf rust also has been observed around the state throughout the winter months. It prefers warmer temperatures around 68-77 degrees; therefore, leaf rust development in wheat fields generally appears as stripe rust is disappearing.
Leaf rust started showing up in the Texas wheat crop in late January. (Texas A&M AgriLife Extension Service photo by Dr. Ron French)
A Texas wheat field with signs of leaf rust. (Texas A&M AgriLife Extension Service photo by Dr. Ron French)
“Both leaf and stripe rust require water on leaf surfaces for spore germination,” he said. “Therefore, moist weather conditions such as heavy dew and rain facilitate disease development, while windy conditions help distribute the fungal spores.”
To effectively control stripe rust, Neely said, growers should know what variety they planted and its resistance level. He said fungicide efficacy trial results can be found at http://varietytesting.tamu.edu/wheat.