Submitted to: Arthropod Management Tests
Publication Type: Research Notes
Publication Acceptance Date: 1/9/2002
Publication Date: N/A
Interpretive Summary: Every year, USDA-ARS curators at the Western Regional Plant Introduction Station, Washington State University, establish field nurseries of grass accessions to replenish seed stocks low in viability and supply. These nurseries are often attacked by aphid pests that have the potential to adversely affect plant health and thus reduce seed production. Although previous research showed that migrating aphids can be the source of some damaging populations, it is not known if some pest aphids overwinter in established nurseries and disperse to new nursery plants in the spring and summer. This research was conducted to answer this question. This three year study demonstrated that pest aphids can overwinter in grass nurseries in eastern Washington state. However, their densities differed greatly from year to year. These findings are important because they underscore the need for constant monitoring of old and new grass nurseries to detect potentially damaging populations of pest aphids.
Technical Abstract: Perennial grass plots of five genera (Agropyron, Elymus, Elytrigia, Pseudoroegneria, and Thinopyrum x Triticum) at Central Ferry, Washington, were colonized by three species of pest aphids over three years. The plot taxa supported very few aphids in 1999 and 2002; however, high populations of Diuraphis noxia and Rhopalosiphum padi were recorded in 2001. R. padi populations were high in Spring 2001 on all entries, indicating significant over-wintering on these grasses. The grass Thinopyrum x Triticum consistently supported more R. padi and D. noxia compared with other grass taxa. Counts of a third aphid, Metapolophium dirhodum, were very low in 2001. Aphid densities were not consistently related to changes in plant biomass on each entry. In summary, perennial grass taxa in this study were suitable hosts for pest aphids and their densities on these grasses differed greatly from year to year.