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Stripe rust still big problem, researchers say

IT’S STRIPED AND LOOKS LIKE RUST: Stripe rust on wheat. The condition can afflict several kinds of crops.

Stripe rust is at it again.

Following high stripe rust levels across the Pacific Northwest (PNW) in 2011, researchers from the U.S. Department of Agriculture (USDA) and crop protection company Syngenta have been carefully monitoring its development during the fall to help growers prepare a defense plan for 2012.

Fall 2011 stripe rust levels ranged from normal to above average across the PNW, so growers are being encouraged to develop a management plan that includes resistant varieties for spring wheat acres and proactive scouting.

Stripe rust is one of the most weather-induced diseases in cereal crop production when weather conditions are wet and warm. This disease is notorious for developing rapidly and causing widespread damage. Across the PNW in 2010, stripe rust-infected, susceptible wheat varieties experienced approximately 60 percent yield loss.

“The stripe rust infection we saw in fall 2010 was the worst in PNW history,” explained Xianming Chen, Ph.D., research plant pathologist at Washington State University.

Infections of stripe rust in fall 2010 began the epidemic recorded in 2011, and its severity continued to escalate throughout the year. Generally, the PNW climate is conducive to stripe rust development, and experts emphasize that weather conditions this winter will ultimately determine disease severity in 2012.

“We experienced close to what we consider a normal situation for this region in November 2011. But you can find stripe rust in the PNW every year—the difference is in the level of infection,” Chen added.

Low moisture levels this past September combined with a late harvest helped decrease the possibility for the disease to “green bridge,” or spread from the harvested crop to newly planted crops. However, if stripe rust did effectively attack wheat leaves this past fall, it has the potential to survive the winter, particularly if this winter is warm and/or wheat fields are consistently covered with snow.

When growers are prepared with a proactive plan to thwart rust infections, crops can thrive during the 2012 season with little disease and strong yields. Experts advise the defense plan focus on three areas—varieties, scouting and fungicides. Growers are encouraged to book their spring wheat varieties early based on resistance performance in recent years and end-use goals. In addition, aggressively scouting for rust after winter will be critical for determining proper fungicide use throughout the season. This process can begin as soon as the snow melts.

“Immediate action growers can take is selecting their spring wheat cultivars. The cultivars grown in the PNW have some level of resistance, but few provide 100 percent control of stripe rust. For non-resistant varieties, we recommend growers spray a fungicide when rust just starts in the field,” Chen explained.

Stripe rust-resistant disease varieties come with varying levels of resistance – from moderate to highly resistant. Experts note that in addition to considering cultivars with good resistance, winter survival rates and yield potential are important variety selection factors to evaluate, as well.

“Across the region, I recommend growers strive to move toward new genetics on their farm and select varieties that have good genetic resistance. It’s also critical to protect those good genetics with top-notch chemistries,” said John Moffatt, Pacific Northwest cereals breeder/manager, Syngenta, Cheney, Wash.

For the 2012 season, Syngenta anticipates releasing SY Ovation, a new soft white winter wheat. The first variety release from Syngenta using double haploid technology, SY Ovation is a very high-yielding, semi-dwarf variety that, according to Moffatt, held up well in trials to the intense stripe rust pressure growers experienced in 2010 and 2011.

“If growers want to maximize yields, it pays to protect their crops against all possible constrictions to final yield. If a fungicide application can be made at herbicide timing, it simplifies the process,” Moffatt noted.

The USDA, Syngenta, and Washington State University will continue to closely monitor the progress of stripe rust and release disease forecast models as the winter continues.


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