Seasonal Abundance and Species Composition of Aphids (Homoptera: Aphididae) in Virginia Small Grains

Abstract

The seasonal abundance of aphids in winter wheat and barley was monitored in eastern Virginia during 1979–1980 and 1980–1981. Significantly more aphids were observed in barley than in wheat. Population densities were significantly higher in the fall of 1979 than in 1980; however, the reverse was noted in springtime population levels. The heavy fall population, approaching 240 aphids per 0.3 row m. rapidly dropped in December 1979 after 8 consecutive days of subfreezing temperatures. The 1980–1981 season had below-normal temperatures in the fall, and populations never exceeded 82 aphids per 0.3 row-m until spring. In both years, aphid populations rapidly fell in May after several days of 27°C temperature and low humidity. The corn leaf aphid. Rhopalosiphum maidis (Fitch), was usually the most abundant species in the complex in autumn. The English grain aphid, Macrosiphum Avenae (F.), was the most abundant species during the spring. Rhopalosiphum padi (L.), and the green bug, Schizaphis graminum (Rondani), were relatively abundant throughout the entire growing season. Corn leaf aphids were not present in the spring. Ovoviviparous reproduction was observed in most months of the season, even at temperatures as low as 9° C.