Lessons from stripe rust tough to tell at this point

What lessons should farmers take from this year’s historically bad stripe rust infection?

Hard to say, according to Xianming Chen, a stripe rust researcher with the United States Department of Agriculture’s Ag Research Service at Pullman.

Chen said the rust infection of 2010 was the most wide-spread on record.

“The way things lined up, it created very favorable conditions for the infection cycles of stripe rust,” he said.

The cool, wet spring that followed a warm end of winter provided the perfect conditions for rust.

Such a pervasive outbreak, with rust sweeping through fields across the Palouse in July, has left behind a number of spores in fields already planted with winter wheat.

Rust spores have already made themselves evident on crops in Montana and Mount Vernon, said Chen, but that is normal for those areas. To see it in Palouse winter wheat is unusual.

“We can see some rust now. It’s hard to see it right now, but if you take a good close look at it you can see it,” said Chen.

But the significance of those now-present spores is a question, he added.

“If we get a warmer winter, then we can have a big problem next year,” said Chen. “If we have a cold winter this year, then it could kill off the rust and next spring it will also start late and may have lighter rust. Now is too early to see.”

Chen put out rust updates throughout the spring and summer, when the rust outbreak really kicked into gear.

Earlier this year, he put out a report breaking down the impact rust made on different varieties of wheat. He said his hope is farmers could use that report to influence their planting decisions.

The danger, he said, is that some farmers will plant varieties with lower yields and of lesser quality in response to this year’s rust.

“It’s important to have that rust resistance, yeah, but sometimes, farmers will sacrifice quality and yields in order to get that,” said Chen. “That’s why we try to tell farmers it’s important to diversify the varieties you plant.”

Xerpha, for instance, took this year’s rust outbreak particularly hard. Xerpha wheat sprayed with a fungicide yielded an average of 95 bushels per acre. Unsprayed Xerpha crops yielded 70 bushels per acre, meaning the fungus ate away 26 percent of yields.

Because of its high yielding, high quality performance of the past few years, Xerpha was one of the most planted varieties. Around the state, farmers planted Xerpha on 159,766 acres, good for nine percent of the state’s wheat crop.

Madsen, the ironman of white wheat, was planted on 95,100 acres in the state.

Madsen fields yielded 110 bushels of wheat when not sprayed for rust. Spray made little difference on Madsen crops, adding just one bushel per acre to the yield.

University researchers’ task now is to take the rust resistant genes in varieties like Madsen and breed them into Xerpha to give farmers the best of both worlds; a high-quality, high-yielding plant that is resistant to rust.

“Even though rust doesn’t hit real hard every year, that resistance needs to be there in case it does,” said Chen.

Same with spring varieties.

Louise, the most commonly planted spring wheat on 163,100 acres, lost 8.5 bushels per acre to rust.

Hank lost the most to rust, yielding 44 bushels per acre when sprayed; 23 bushels per acre unsprayed.

Chen added breeding rust-resistance into susceptible varieties will be vital to farmers in the face of unpredictable weather patterns.

“It’s either that or we build a weather machine,” he chuckled.