Who-done-its?
Researchers unravel mysterious worlds of weeds and global pests
AS WITH VIRTUALLY ALL commercially grown farm crops, unending battles involve weeds that crowd out the food crop and pests that maim and even destroy crops. For University of Idaho wheat scientists and extension educators, these villains never disappear. They only evolve.
Former UI wheat breeder Ed Souza, who now leads the USDA Agricultural Research Service’s Soft Wheat Quality Laboratory in Wooster, Ohio, takes pride in the disease resistance of Idaho varieties he developed while working at Aberdeen. “All of them went out the door with solid resistance to dwarf bunt, the winter wheats had good resistance to snow mold, and the stripe rust resistance in Alturas is still good.”
Stripe rust & Hessian fly
Several years ago, when an unexpected cascade of new stripe rust races broke resistance in many of the region’s wheat varieties—particularly its soft white springs—Moscow-based wheat breeder Robert Zemetra says the UI CALS’ statewide field trials proved their merit.
“Because we’ve had dependable and continuous funding from the Idaho Wheat Commission (IWC) and have always been selecting against stripe rust, we could identify material that will lead to stronger resistance in the future.”
In Potlatch, IWC commissioner Joe Anderson calls Hessian fly the most significant insect impediment to northern Idaho wheat production. “When we have it, resistant varieties are really the only control mechanism,” he says. Using both traditional laboratory screening and molecular markers, Souza, Zemetra, and UI entomologist Nilsa Bosque-Pérez produced the Hessian fly-resistant varieties Cataldo and Jerome, each of which carries a different gene for resistance. Down the road, they anticipate varieties with multiple or “stacked” resistance.
Bosque-Pérez also surveys fields for Hessian fly and its natural enemies and examines the effects of tillage practices on fly biology. In addition, she compares populations of beneficial carbid beetles in no-till versus conventional crops.
Russian wheat aphid
When the potentially devastating Russian wheat aphid entered Idaho in 1988, IWC support supplemented USDA funding for a multidisciplinary response. Short-term solutions included developing pest-monitoring systems like suction traps and field sampling methods as well as effective insecticidal control.
Faculty, staff, and students worked on longer-term sustainable-management strategies, such as developing and introducing biological control agents and identifying germplasm from countries like Iran and Iraq that carried genetic resistance to the Russian wheat aphid. By 1996, the Russian wheat aphid was only a sporadic and localized pest.
Those pesky weeds.
Herbicide development was Donn Thill’s top priority when he arrived on the Moscow campus in 1980. “The last 50 years have been a remarkable time as far as weed management in wheat,” says Thill, now superintendent of the university’s Moscow-based Palouse R&E Center. As resistance to herbicides evolve in targeted weeds, he forestalls weed resistance through development of new weed management practices.
Now, he’s following a series of educational publications with a computer program, “Herbicide Resistance and Persistence,” that guides growers in selecting herbicides least likely to fuel resistance in their crop rotations. And, he has stepped up studies of herbicide-resistant Italian ryegrass, which some northern Idaho growers find can no longer be controlled with currently registered herbicides.
Souza credits Thill’s “year-in and year-out evaluations” for Idaho weed management as being “much more sophisticated” than in the eastern U.S.
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