Soybean aphid predators in Quebec and the suitability of Aphis glycines as prey for three Coccinellidae

Since its invasion of North America in 2000, the soybean aphid, Aphis glycines Matsumura (Homoptera: Aphididae) has notably changed the arthropod community of the soybean agroecosystem. The objectives of this study were to characterize the foliar predatory fauna associated with A. glycines in commercial soybean fields in Quebec, Canada, and to evaluate the suitability of A. glycines as prey for three coccinellid species: Harmonia axyridis Pallas, Propylea quatuordecimpunctata L. and Coleomegilla maculata lengi Timberlake ( Coleoptera: Coccinellidae). Field surveys showed that several predators responded rapidly to expanding and increasing populations of the soybean aphid. Coccinellidae were the most important aphidophagous predators observed in 2002 (58.6%) and 2003 (44.8%), with mainly four native and naturalized species co-occurring with the soybean aphid throughout the growing season. Measurement of fitness parameters under laboratory conditions ( survival, development time, longevity, fecundity) indicated that A. glycines is an excellent prey for the development and reproduction of all three of the coccinellid species studied. The intrinsic rate of natural increase (r(m)) was highest for H. axyridis (0.238 d(-1)), intermediate for P. quatuordecimpunctata (0.215 d(-1)) and lowest for C. maculata (0.134 d(-1)).