“Juliet was a moving force in getting farmers to do something. She was key in alerting us to the movement of the disease. We were able to get some fungicide on our crop when it needed it.”
Dwight Little, Newdale farmer and
member of the Idaho Barley Commission
Story by Dave Wilkins; photo by Pam Benham
Wheat and barley growers in arid southern Idaho are fortunate that they seldom have to worry about stripe rust. They can also be thankful that they have someone like Juliet Marshall to warn them when conditions are perfect for the fungal disease to explode—as they were in 2011.
Growers who responded are glad they did.
Marshall, a University of Idaho Extension cereal pathologist based in Idaho Falls, became concerned last fall when she noticed stripe rust in the winter wheat variety trials at the University of Idaho’s Aberdeen Research and Extension Center 65 miles to the southwest.
“I had never seen that before,” she said. It’s a worry for Magic Valley and eastern Idaho growers whose farm gate value for wheat and barley topped $590 million in 2010.
Worldwide peril of rust diseases
Rust diseases are among the most widespread and economically damaging in cereal crops worldwide. Characterized by the yellow-orange lesions that form stripes on infected leaf blades, stripe rust rarely survives southeastern Idaho’s frigid winters, but Marshall knew it was a possibility. Because of the fall infection, she started warning growers of the threat during UI-sponsored cereal schools in February 2011. Marshall collected leaf samples from her plots as soon as the snow melted in spring 2011 and put them under the microscope.
The presence of viable spores told the story: Stripe rust had survived winter. “That raised a huge red flag,” Marshall said. “I put out a stripe rust alert at that point.” Marshall routinely issues regular updates to keep several hundred growers and crop advisers informed. She strongly urged producers to take action or risk significant yield losses. UI Extension educators Reed Findlay, Joel Packham, and Lance Ellis also helped identify infected fields and distributed information on control.
The outbreak was so severe this year that yield reductions of 10 to 20 percent were reported even among growers who sprayed twice.
photo by Dave Wilkins
At Aberdeen, Marshall documented yield reductions of nearly 80 percent in some winter wheat varieties that were left untreated compared with those in replicated plots that were sprayed twice. The cereals crew, Tod Shelman, Chad Jackson, and Linda Beck, modified the variety trials at Aberdeen to become a stripe-rust-disease trial. Brundage, a soft white wheat, and Moreland, a hard red variety, were among the hardest hit. “I think our average yield loss over all varieties was 40 percent this year, and that’s very unusual,” she told a visiting Ethiopian trade team in August.
“Juliet was a moving force in getting farmers to do something,” said Dwight Little, a farmer from Newdale and a member of the Idaho Barley Commission. “She was key in alerting us to the movement of the disease. We were able to get some fungicide on our crop when it needed it.”
In the Declo area, growers who heeded the alert and applied protective fungicides harvested about 110 to 120 bushels per acre on their irrigated winter wheat fields. “Those who didn’t listen are cutting 60 to 80 bushels,” local grower Mark Darrington said during his August harvest.
The economic impact of that 40- to 50-bushel difference looms large in a year with strong wheat prices. “I would say that that pays for Juliet pretty quickly,” Darrington said.
SHE DOESN'T ISSUE CRPO PEST ALERTS ON A WHIM
Marshall knows that at nearly $20 per acre (chemical costs, plus crop duster service), the cost of commercial aerial applications can add up quickly.
“I’m not a believer in putting on fungicides if you don’t need them,” she said. Marshall, promoted to associate professor rank in 2010 after making tenure, became fascinated with plant pathology in undergraduate school. She revels in uncovering the genetic and environmental complexities of plant diseases. “To me it’s a hidden world,” she said.
Why stripe rust now?
Stripe rust has plagued wheat growers in northern Idaho for years, with its wetter weather, until scientists developed rust-resistant wheat varieties. In dryer southeastern Idaho, a combination of factors made this one of the worst years for stripe rust in recent memory. The rare overwintering of the pathogen and an unusually cold, wet spring played huge roles. “The key to this whole epidemic was that it was the coldest April, May, and first two weeks of June on record for which we had ever analyzed. It was perfect for stripe rust to go crazy,” she said. Support scientist Chad Jackson helped compile the weather data.
This isn’t the first time Marshall has warned growers of a potentially serious stripe rust outbreak. She provided a similar service in 2005. That was the first significant stripe rust outbreak in southern Idaho in many years and Marshall’s first summer on the job.
“That really launched her as a highly credible authority,” said James “Ding” Johnson, Moscow, head of the CALS Department of Plant, Soil, and Entomological Sciences. Plant pathology is just one of Marshall’s responsibilities. She is also the regional cereal agronomist and participates in applied research through variety trials sponsored by the Idaho wheat and barley commissions.
“Juliet is essentially doing the jobs of two people,” Johnson said. Such multi-tasking has become necessary because of budget cuts. “Marshall’s exemplary work on stripe rust this year is a vivid example of the value that University of Idaho Extension provides to Idaho agriculture,” Johnson said.
By press time, Marshall had sent growers an e-mail warning that “this year is setting up to be a lot like last year,” followed by suggestions to prevent infection this fall. If stripe rust does overwinter again, Marshall will be watching.
Contact Juliet Marshall at Juliet.Marshall@uidaho.edu. Also see UI Exgtension Cereals Program for Southcentral and Sougtheastern Idaho www.extension.uidaho.edu/scseidaho/
Dave Wilkins firstname.lastname@example.org is a freelance writer based in Twin Falls.