Yield response to Russian wheat aphid (Hemiptera: Aphididae) in three resistant wheats in eastern Colorado

A study to determine the effect of Russian wheat aphid on yield of resistant winter wheat cultivars was conducted during the 2001-2002 growing season at three locations in eastern Colorado (Akron, Fort Collins and Lamar). Two wheat cultivars resistant to Russian wheat aphid Biotype 1,`Ankor' and `Stanton' were compared to `Halt' (resistant) and `Akron' (susceptible) for yield differences at three infestation levels (OX, 1X and 1 OX) of Russian wheat aphid. All three resistant cultivars supported significantly fewer Russian wheat aphid per tiller than the susceptible `Akron' at all three sites. The number of Russian wheat aphid per tiller negatively affected seed weight for `Akron' at all three sites and for `Stanton' at Akron and yield for `Akron' at both Akron and Fort Collins and for `Ankor' and `Halt' at Akron. `Ankor' and `Stanton' are good Russian wheat aphid Biotype 1 resistant wheat choices for areas with historically high Russian wheat aphid infestations.