Yield Losses in Spring Barley Caused by Cereal Aphids (Homoptera: Aphididae) in South Dakota

Yield losses in ‘Larker’ spring barley, Hordeum vulgare L., due to feeding of Schizaphis graminum (Rondani), Macrosiphum avenae (F.), Rhopalosiphum padi (L.), and R. maidis (Fitch) were measured in 1979, 1980, and 1984 in South Dakota fields. Caged plots were artificially colonized with aphids for 10 days when plants were in three different growth stages; losses in components of yield were measured at harvest. Greatest losses in yield were caused by aphids feeding during the seedling (2–3 leaf) stage; mean densities of 25–30 aphids per stem resulted in losses of 50% in some components of yield at this stage. Lower yield losses were recorded for similar aphid population densities when aphids fed during the boot stage (immature inflorescence invested in leaf sheath) and no losses were observed when plants were mature (dough stage). S. graminum and R. padi were more damaging than M. avenae or R. maidis at similar population densities. Populations of R. maidis developed only in the furled leaves of the growing tip.