|Youssef, N. - TENNESSEE STATE UNIV|
|Evans, M - WASHINGTON STATE UNIVERSI|
Submitted to: Journal of Kansas Entomological Society
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: January 19, 2004
Publication Date: August 3, 2004
Citation: Clement, S.L., Elberson, L.R., Youssef, N., Young, F.L., Evans, M.A. Cereal aphid and natural enemy populations in cereal production systems in eastern washington. Journal of Kansas Entomological Society. 2004. V.77(3). P.65-173. Interpretive Summary: The economic viability of the soft white winter wheat-summer fallow rotation production system in eastern Washington is challenged by wind and water erosion on fallow ground, by invasive weeds, and by diseases. A shift from this production system to continuous no-till spring wheat would ameliorate these problems, but spring-planted cereals are at greater risk of aphid-induced injury than fall-seeded crops. This five year study on a commercial farm in eastern Washington showed that damaging aphid populations are unlikely to develop in winter wheat, but cereal aphids like the English grain aphid in spring cereals warrant monitoring because they fluctuate from year to year and can be damaging. This research also establishes the presence of an introduced lady bird beetle species in eastern Washington for biocontrol of cereal aphid pests, and documents the decline of Russian wheat aphid infestations in Washington wheat fields since this aphid first appeared in the late 1980s. This research is important because it underscores the importance of conducting multi-year field studies to ascertain the potential for cereal aphids to damage winter and spring cereal crops.
Technical Abstract: A 5 year study in the semiarid wheat production region of eastern Washington documented the relative densities of pest aphids and their natural enemies in cereal production systems using on-farm replicated plots. The systems were reduced-tillage soft white winter wheat (SWW) (Triticum aestivum L.) ' summer fallow rotation; no-till soft white spring wheat (SWS) ' chemical fallow rotation; continuous no-till hard red spring wheat (HRS); and no-till HRS ' no-till spring barley (SB) (Hordeum vulgare L.) rotation. The English grain aphid, Sitobion avenae (F.), was the dominant species, followed in abundance by the Russian wheat aphid, Diuraphis noxia (Modvilko). The bird cherry-oat aphid, Rhopalosiphum padi (L.), and rose grass aphid, Metopolophium dirhodum (Walter), were infrequently encountered. Overall, aphid densities were low, with aphids rare or absent in SWW and SB plots. The data revealed no clear and consistent effects of cereal production systems on aphid densities, but it did reveal, based on analysis of data from continuous HRS plots, high among-year variability in S. avenae and D. noxia densities. Only in 1996 and only in continuous HRS was it necessary to chemically control damaging populations of D. noxia. English grain aphid densities never approached threshold levels. S. avenae parasitism averaged >16% in some spring wheat systems in 1998 and 2000, while only two mummified D. noxia were observed. Coccinellid beetle counts in all plots totaled 143 in 1998 and 163 in 2000, with 90.2% and 94.5% in the genus Hippodamia, respectively. The lady bird beetle Coccinella septempunctata L. comprised 9.8% (1998) and 5.5% (2000) of the populations. The results suggest that damaging aphid populations are unlikely to develop in winter wheat, but populations in spring cereals warrant monitoring because they fluctuate from year-to-year and can be damaging.