Abundance of Two Whitefly Species (Homoptera: Aleyrodidae) on Georgia Soybean

‘Braxton’ and ‘Cobb’ soybeans were surveyed every 7 to 10 days from mid-July through September, 1993 and 1994, to determine the seasonal abundance of the silverleaf whitefly, Bemisia argentifolii Bellows and Perring, and the bandedwinged whitefly, Trialeurodes abutilonea (Haldeman). Population densities peaked in early September 1993, at over 31 eggs and nymphs per 2.54 cm² of leaf area on Cobb soybeans (a Maturity Group VIII variety), and 15 eggs and nymphs on Braxton soybeans (a Maturity Group VII variety). Silverleaf whitefly was the predominant species on all sampling dates throughout the season. At the population peak, there were 14.4 silverleaf whitefly and 3.3 bandedwinged whitefly nymphs per 2.54 cm² on Cobb and 8.8 silverleaf whitefly and 2.0 bandedwinged whitefly nymphs on Braxton. Whitefly population densities peaked in late September 1994, at over 6 eggs and 59 nymphs on Cobb and 1 egg and 18 nymphs on Braxton. The whitefly population in 1994 was comprised almost exclusively of silverleaf whitefly, with 58 and 17 nymphs per 2.54 cm² on Cobb and Braxton, respectively, on 23 September compared to less than 1.0 bandedwinged whitefly on each of these varieties. At the population peak each year, there were significantly more eggs and silverleaf whitefly nymphs on the upper trifoliolate leaves than on the lower trifoliolate leaves.