Comparison of host suitability of western wheat aphid with the Russian wheat aphid

The western wheat aphid, Diuraphis tritici (Gillette), and the Russian wheat Diuraphis noxia (Mordvilko), are pests of wheat, Triticum aestivum L. Both species similar distribution pattern in the United States. However, D. noxia is a perennial economic pest of wheat, whereas D. tritici is, at most, an occasional economic pest of wheat. The economic importance of D. noxia depends in part on its ability to use alternative plant species as oversummering hosts. We studied the survival and reproduction of D. tritici on numerous cool- and warm-season grasses, legumes, and forbs, and also compared D. tritici with D. noxia on some common Bromus spp. and Agropyron spp. to see if the 2 aphid species differ in their reproduction and survivorship on the same grass species. D. tritici survived on 36 of 40 cool-season grass species, 7 of 19 warm-season grass species, and none of the 33 legumes or 13 forbs. The natality of D. tritici compared with D. noxia on several species of brome grasses and wheatgrasses was generally significantly lower for D. tritici than D. noxia. D. tritici preferred wheat compared with 3 other cereals, whereas wheat and barley were equally suitable as hosts for D. noxia. Rye, Secale cereale L., was essentially a nonhost for D. tritici. After 14 d, aphid populations were significantly higher for D. noxia on all 4 cereals compared with D. tritici populations on the same hosts. In a separate experiment to compare damage of D. tritici with D. noxia on different growth stages of wheat, we found that D. tritici was significantly more deleterious than D. noxia to the yield potential and yield components of wheat, particularly when infestation occurred at the 7-leaf plant growth stage and the jointing growth stage. The economic importance of D. noxia compared with D. tritici to U.S. wheat production may be caused in part by its ability to survive and increase on cool-season grasses and cereals better than D. tritici.