The strategy can carry some costs. Delayed seeding may reduce yield potential in the absence of disease. But the risk is better than the almost-all or nothing gamble of planting too early and suffering devastating losses if the aphids find a field of freshly emerged seedlings. Mites carry the wheat streak mosaic virus. Wheat growers must try to break the green bridge of live wheat or grasses growing nearby that permit the mites to move into a newly emerged field.
Growers disk under any volunteer wheat or grass plants at least two weeks before sowing.
UI scientists have taken up the gene gun in hope of an alternate defense. At Moscow, plant pathologist Phil Berger and wheat breeder Bob Zemetra teamed up to try to insert viral resistance directly into established wheat varieties. Although the two viruses are particular targets, the researchers also want to insert generic viral resistance into wheat. DNA carrying the resistance is shot into wheat embryos using a gene gun. Berger then evaluates the plants for viral resistance and Zemetra evaluates their desirable characteristics, such as yield and end-use quality.