Stripe rust pustules

Two small stripe-rust pustules are shown on a winter-wheat leaf.

Cool weather made Nebraska’s wheat crop late to green up this year, but the lower temperatures helped in other ways.

Yields benefited from a long filling period and ample rain, according to wheat expert Robert Klein, who covers the west-central part of the state for the University of Nebraska-Lincoln Extension. It was having enough precipitation that made the crop, he said.

“That’s always the most critical thing and most limiting in crop production,” he said.

Disease pressure was hit or miss through the Midwest. Klein had reports of a little head scab and fusarium head blight, but rust wasn’t as bad as in past years.

“It got to us a little bit late here to really do some damage,” Klein said.

That was the case for stripe rust – one of the three major types of rust that affect wheat. Stripe rust favors cool temperatures, so it’s usually a problem early in the season. This year, it was spotted May 30 in south central Nebraska, but because it came late when temperatures were starting to warm it didn’t develop into much of a problem, according to Stephen Wegulo, UNL Extension plant pathologist based in Lincoln.

Stem rust posed very little threat as well. Wegulo heard reports of stem rust in two UNL breeding plots, one in Lincoln and one in Sydney in the southern panhandle.

Leaf rust was the biggest problem this year. It was spotted in late May and infections became pretty severe in some fields around June 10, Wegulo said. South central Nebraska and the southeast saw the worst of it, but fungicide treatments provided some relief.

“Many growers were really on their feet on the lookout and sprayed,” Wegulo said, adding that rust could hardly be seen in fields that were sprayed.

South Dakota wheat growers saw more rust than usual this year. With fields to the north a little behind their Nebraskan neighbors, rust hit with some strong southern winds in June. Issues weren’t severe, according to Syngenta agronomist Wally West, who is based in Brandon, South Dakota, but the problem was worse than average, and fields might show a little yield loss because of it.

Rust doesn’t overwinter in colder climates. It blows in from southern states. Websites help growers monitor the threat, and fungicides can help combat the disease. It should be a priority to protect the flag leaf from rust, West said. It’s the last leaf to emerge before the wheat head, and it generates roughly 40% of the energy that goes into the wheat seed, he said.

Growing varieties that are bred to be rust tolerant is the first step in standing up to the disease, West added.

Rust reproduces a new generation every 10 days. The changing genetics make it difficult to breed resistant wheat varieties and develop effective fungicides. West suggests using a fungicide with a strong residual.

Researchers at the University of Minnesota have been taking a new approach to fighting rust and other wheat diseases. A study published earlier this year in the journal Nature Biotechnology detailed a new method for cloning disease resistant genes.

Instead of focusing on one disease, scientists from the University of Minnesota and colleagues in England and Australia targeted an entire DNA sequence in wild wheat that can fight against several diseases. Researchers isolated four resistance genes within six months, where the process would normally take a decade or more for a single gene.

University of Minnesota Plant Pathology Professor Brian Steffenson, a co-lead on the project, called it a significant breakthrough.

“(It) will facilitate and accelerate the development of more durable, resistant varieties not only for wheat but many important crops,” Steffenson said in a news release.

Incorporating many resistance genes into a wheat variety would help one major issue with today’s resistant varieties – that they’re effective for about five years.

In that time, the rust pathogen can mutate, making previously resistant wheat varieties vulnerable to rust.

“This genetic engineering protocol may usher in a new revolution of plant breeding where crops can be made more resilient to withstand the onslaught of pathogens and insects alike,” Steffenson said.

It’s not possible to predict what rust pressure will look like next year. Levels depend on development in the South, Wegulo said, but there’s usually some idea of the threat by February.

Klein stresses that growers should start with fields clear of weeds and volunteer wheat, which can use soil moisture the next crop needs to grow.

West urges producers to start planning for next year by taking notes on which fields and which varieties did well this season.

“All of that matters when the time comes to make decisions for next year on how to produce a stronger, better yielding crop,” he said.

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Janelle is editor of the Tri-State Neighbor, covering South Dakota, southwestern Minnesota, northwestern Iowa and northeastern Nebraska. Reach her at jatyeo@tristateneighbor.com or follow on Twitter @JLNeighbor