Reproduction and development of Russian wheat aphid biotype 2 on crested wheatgrass, intermediate wheatgrass, and susceptible and resistant wheat.

The Russian wheat aphid, Diuraphis noxia (Kurdjumov), is an economically important pest of small grains. Since its introduction into North America in 2003, Russian wheat aphid Biotype 2 has been found to be virulent to all commercially available winter wheat, Triticum aestivum L., cultivars. Our goal was to examine differences in Russian wheat aphid reproduction and development on a variety of plant hosts to gain information about 1) potential alternate host refuges, 2) selective host pressures on Russian wheat aphid genetic variation, and 3) general population dynamics of Russian wheat aphid Biotype 2. We studied host quality of two wheatgrasses (crested wheatgrass, Agropyron cristatum [L.] Gaertn., and intermediate wheatgrass, Agropyron intermedium [Host] Beauvoir) and two types of winter wheat (T. aestivum, one Biotype 2 susceptible wheat, 'Custer' and one biotype 2 resistant wheat, STARS02RWA2414-11). The susceptible wheat had the highest intrinsic rate of increase, greatest longevity and greatest fecundity of the four host studied. Crested wheatgrass and the resistant wheat showed similar growth rates. Intermediate wheatgrass had the lowest intrinsic rate of increase and lowest fecundity of all tested hosts.

Categories of resistance at four growth stages in three wheats resistant to the Russian wheat aphid (Homoptera: Aphididae).

Laboratory experiments were conducted to determine categories of resistance to Russian wheat aphid, Diuraphis noxia (Mordvilko), in three wheats, Triticum aestivum L, (PI 372129, PI 243781, and PI 222668) at Zadoks growth stages 10, 20, 30, and 40. 'TAM 107' was used as the susceptible standard. Antixenosis was observed in PI 222668 and PI 372129. Antibiosis was expressed as reduced nymphipositional period, daily nymph production, and fecundity at the jointing (Zadoks 30) and boot (Zadoks 40) stages in PI 243781 and at tillering (Zadoks 20) in TAM 107. Antibiosis, expressed as reduced intrinsic rate of increase, was observed in PI 222668 at tillering (Zadoks 20). Tolerance to chlorosis and leaf rolling was expressed in the three resistant wheats at all growth stages tested. Tiller production, floret formation, spike length and wet weight were affected by Russian wheat aphid feeding after Zadoks 10. Reduction in spike length did not occur in PI 372129 and PI 243781.