Field populations of cereal aphids in South Dakota spring grains.

Studies of field populations of cereal aphids in spring small grains in South Dakota (1963–72) showed that Schizaphis graminum (Rondani), Macrosiphum avenae (F.), and Rhopalosiphum padi (L.) commonly colonized wheat, barley, and oats; R. maidis (Fitch) was found only in barley and only while the developing leaf blades were still furled. S. graminum often was present during a greater proportion of the season than the other species. Populations of all species were predominantly nymphal throughout the season with substantial numbers of alatae (migrant) only present as founders of colonies early in spring. S. graminum was distributed nearly randomly within fields, but M. avenae and R. padi were distinctly aggregated.