Russian wheat aphid (Homoptera: Aphididae) reproduction and development on five non-cultivated grass hosts

The Russian wheat aphid, Diuraphis noxia (Kurdjumov) is an invasive species which is economically detrimental to small grain production. While eight Russian wheat aphid biotypes have been identified in the United States, these populations have only been found to reproduce parthenogenetically. Recently discovered genetic diversity raises concerns that additional biotypes may be virulent to future cultivars deploying new sources of resistance. Genetic diversity may be attributed to selection pressure imposed by non-cultivated grass hosts, or holocycly triggered by the harsher winter conditions at higher elevations. The goal of this study was to observe the host quality of five grass species commonly utilized by the Russian wheat aphid at higher elevations, as measured by intrinsic rate of increase. Grass species tested were intermediate wheatgrass (Elytrigia intermedia Nevski), crested wheatgrass (Agropyron cristatum L.), slender wheatgrass (Elymus trachycaulus), western wheatgrass (Pascopyrum smithii A. Love), and foxtail barley (Hordeum jubatum L.). Life statistics were measured on each grass species in a growth chamber at a temperature regime of 18-24°C with a photoperiod of 14:10 (L:D) h. Diuraphis noxia life statistics, including fecundity, longevity, pre-nymphipositional period, nymphipositional period, generational time, and intrinsic rate of increase, were calculated and compared among hosts. Russian wheat aphids on all grass hosts had positive intrinsic rates of increase, but all values were below those previously reported for resistant and susceptible wheat. Aphids feeding on western wheatgrass had the lowest intrinsic rate of increase, indicating high selection pressures.