Russian wheat aphid, Diuraphis noxia (Kurdjumov), falling rates from resistant and susceptible wheats

Russian wheat aphid, Diuraphis noxia (Kurdjumov), is an important pest of wheat in Colorado, and generalist predators are abundant in wheat agroecosystems. The proportion of Russian wheat aphids that fall to the ground from resistant and susceptible wheat plants was measured as part of an effort to assess the potential of ground predators as aphid biological control agents. Falling rates of Russian wheat aphids were observed in wheat plots from May-July 2008 in Akron and Ft. Collins, Colorado. One experimental Russian wheat aphid-resistant wheat line and a susceptible sister line were planted in eight replications at each site. The wheat within each plot was artificially infested with one of two levels of aphids, 1x or 10x. Traps consisting of Plexiglass squares with areas of 182 cm² at Akron and 141 cm² at Ft. Collins were coated with Tanglefoot® and were used to capture aphids. The traps were placed on the ground between wheat rows in each plot and were run for 24 hours every other week at each site. Wheat tillers from each infestation level were sampled to estimate aphid abundance on plants. We hypothesized that the falling rate would be highest in the aphid-resistant cultivar plots at the 10x infestation level. We will discuss results with an emphasis on whether the falling rate of the Russian wheat aphid suffices to supply ample prey for ground predators.