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Title: Occurrence of hymenopterous parasitoids of Diuraphis spp. in the western Rocky Mountain region

Author
item Burd, John
item Puterka, Gary

Submitted to: Southwestern Entomologist
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/1/2011
Publication Date: 6/1/2012
Citation: Burd, J.D., Puterka, G.J. 2012. Occurrence of hymenopterous parasitoids of Diuraphis spp. in the western Rocky Mountain region. Southwestern Entomologist. 37(2):231-234.

Interpretive Summary: Four species within the genus Diuraphis occur in the western United States. The Russian wheat aphid, Diuraphis noxia Kurdjumov, an invasive species which was first detected in the United States in the spring of 1986, is the only economically important one of this group. The other three species are D. frequens, D. mexicana, and D. tritici, which are indigenous and occur primarily on wild grasses. The natural enemy complex of the Diuraphis spp. is not well known and scant information is available regarding their hymenopterous parasitoids. Surveys were conducted from September through October of 2007 and 2008 to identify the hymenopterous parasitoids attacking Diuraphis spp. in the westcentral Rocky Mountain Region of the United States. Overall, Aphelinus albipodus was the main parasitoid of all Diuraphis spp. and was the only parasitoid found to attack D. mexicana and D. tritici. The other two aphelinids recovered were much more restricted in their distributions. Diaeretiella rapae was the most widespread aphidiid; however, it was only recovered from D. noxia and D. frequens. Except for Lysiphlebus testaceipes, all of the recovered parasitoids were exotic and were imported and released to aid in the control of the invasive D. noxia. A. albipodus, A. asychis, and D. rapae have become established and widely distributed throughout the range of D. noxia in the central Great Plains; however, this is the first report of their distribution in the western Rocky Mountain region. Moreover, this is the first reported recovery of A. colemani and E. plagiator from D. noxia in Colorado.

Technical Abstract: Four species within the genus Diuraphis occur in the western United. The Russian wheat aphid, Diuraphis noxia Kurdjumov, an invasive species which was first detected in the United States in the spring of 1986, is the only economically important one of this group. It is the most prevalent species of Diuraphis and is a perennial pest of wheat (Triticum aestivum L.) and barley (Hordeum vulgare L.) in the cereal production regions of the Great Plains. The other three Diuraphis spp. are indigenous and occur primarily on wild grasses. Diuraphis frequens (Walker) has been collected from several grass species, including wheat, but is most commonly found on blue wildrye (Elymus glaucus Buckley). The western wheat aphid, Diuraphis tritici (Gillette), which has on rare occasion caused localized economic loses of wheat, primarily colonizes wild grasses, most frequently mountain brome (Bromus marginatus Nees ex Steud). Finally, Diuraphis mexicana (Baker) which has not been reported to colonize cultivated cereal has the most narrow host range, occurring only on Bromus spp.