Wheat farmers across the U.S. might be in for another challenging year. The wind is blowing spores from Texas north and farmers need to be prepared to scout and take action.
“They (stripe and leaf rust) overwinter in Texas and Mexico,” says Clark Neely, Texas A&M statewide small grains and oilseed Extension specialist. “We had a milder winter which could be why we’re seeing it further north.”
In 2015 wheat stripe rust ran rampant across wheat growing acres. Texas lost a cumulative total of about 25% of their yield to the disease. So far, this year is following in suit and could bring similar losses if weather conditions allow.
Right now farmers are seeing stripe rust, which favors cooler, wet conditions and attacks the lower canopy leaves first. While scouting for stripe rust identify it by bright orange to yellow pustules. The pustules form circle patterns in early stages and eventually become a stripe pattern on leaves as the fungus progresses. Stripe rust will be especially devastating in susceptible wheat varieties, Neely says. “Farmers can have up to 85% yield loss.”
Over the next few weeks if your area has moist conditions, such as rain, heavy dews or fogs, and is between 50° and 59° Fahrenheit be sure to diligently scout as stripe rust favors those conditions.
2016 Stripe Rust Risk
Darker states indicate stripe rust has already been discovered and places them at higher risk. Lighter states are at risk of spores spreading via wind and infecting plants.
Unlike stripe rust, which only appears when conditions are right, leaf rust tends to pop up every year in at least one location. The disease is less damaging than stripe rust but can still cause up to 50% yield loss in susceptible varieties, Neely says.
Typically, wheat farmers probably don’t see leaf rust quite yet since it favors warmer temperatures of 60° Fahrenheit and higher—really flourishing at 70° Fahrenheit (ceasing at 80° Fahrenheit). Identify leaf rust by brown to dark red pustules in random patterns across lower canopy leaves. The fungus is temperature driven and can appear during any growth stage.
You might see leaf rust this year. A mild winter might have allowed some spores to overwinter in Texas and Oklahoma. Consider scouting once weekly if temperature and moisture conditions favor the development of leaf rust. Be especially meticulous during flagleaf since the pathogen can steal the greatest amount of yield at this time.
Leaf rust, sometimes called brown rust is identified by brown to dark red lesions in random patters on the lower leaves. Courtesy of Clark Neely
What can you do to avoid rusts?
“The No. 1 thing we encourage is find a resistant variety,” Neely says. “It’s not foolproof but it provides a big level of protection. It could take you from 85% to 25% yield loss.”
Fungicides are another tool that can help you mitigate yield loss by slowing or stopping pustules from spreading and further damaging leaf tissue. Neely says if pressure is high early in the season you can apply a more inexpensive fungicide in early stages and then decide if the crop will yield enough to justify application in later stages with a more pricey fungicide.
2015 Yield Loss From Stripe Rust
2015 was a challenging year for wheat farmers. This map indicates yield loss attributed to stripe rust.
Are you seeing stripe rust in your fields now? What is your plan for stripe and leaf rusts if they make their way into your fields?