|Elliott, Norman - Norm|
Submitted to: Southwestern Entomologist
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/10/1997
Publication Date: N/A
Interpretive Summary: The Russian wheat aphid is a serious insect pest of wheat and small grains in the Great Plains. Efforts are underway to develop strategies for controlling this pest, including the use of parasitoids and predators (biological control). Aphelinus asychis (Walker) was imported to the United States from three different geographic areas for potential use in classical lbiological control programs. Temperature requirements for development of A asychis colonies from two geographic regions (hereafter referred to as strains) were measured using the Russian wheat aphid as the host species. Three strains of the parasitoid from Pingluo, China; Dmitrievka, Kazakhstan; and Sette, Morocco were reared on Russian wheat aphids and evaluated for their ability to parasitize hosts of 16 different aphid species that commonly occur in agricultural landscapes in the Great Plains. We found that developmental threshold values for A. asychis were higher than those for Russian wheat aphid and its aphidiid parasitoids, indicatin poor adaptation to climate. Although it may not inhibit establishment, the dissimilarity between the Russian wheat aphid and A. asychis may limit the parasitoid's effectiveness as a biological control agent. The successful development of A. asychis on several aphid species inhabiting common plants in the Great Plains suggests potential for successful field establishment, although the broad host range of the parasitoid may also restrict its effectiveness.
Technical Abstract: Aphelinus asychis (Walker) was imported to the United States from three different geographic areas for classical biological control of the Russian wheat aphid, Diuraphis noxia (Mordvilko). Temperature requirements for development of A. asychis colonies from two geographic regions (hereafter referred to as strains) were measured using the Russian wheat aphid as the host species. Lower temperature thresholds for immature development were 8.16 and 9.33 deg C, respectively, for laboratory colonies established from the parasitoid strains collected near Pingluo, China, and Sette, Morocco. Degree-day requirements for development from the egg to the adult stage were 230.3 and 195.4 for the two strains, respectively. Three strains of the parasitoid from Pinglou, China; Dmitrievka, Kazakhstan; and Sette, Morocco were reared on Russian wheat aphids and evaluated for their ability to parasitize hosts of 16 different aphid species that comonly occur in agricultural landscapes in the Great Plains. The Chinese and Moroccan strains successfully parasitized 15 of the 16 aphid species; the Kazakhstan strain of A. asychis parasitized 14 of 16 species. All strains showed high adult emergence rates (97-100%) on Russian wheat aphids. However, when emergence rates were averaged over all acceptable host species, the Chinese strain (98%) had significantly higher emergence rates than the Kazakhstan strain (86%), while it was not different from the Moroccan strain (96%).