SURVIVAL, DEVELOPMENT, AND REPRODUCTION OF TURNIP APHIDS (HOMOPTERA, APHIDIDAE) ON OILSEED BRASSICA

Fecundity, survival rate, and days to maturity of turnip aphids, Lipaphis erysimi (Kaltenbach), were studied on 10 accessions of Brassica spp. that had only moderate damage ratings when compared with 'Toria-A'(Brassica campestris L. cultivar) and K-841 (Eruca sativa Miller breeding line). Clip cages confined the developing nymphs and reproducing adults on the leaves of these oilseed accessions. Fecundity of turnip aphids was significantly lower on UCD-310/3 and K-841. Survival of nymphs was significantly lower on UCD-12/4, UCD-6/13, and K-841. Turnip aphids took fewer days to mature on 'Toria-A' than on UCD-310/3, K-841, UCD-6/24, and UCD-12/4. The r(m) value for turnip aphids was significantly higher on 'Toria-A' than on all other accessions, whereas it was lowest on UCD-310/3 and K-841. In an experiment to determine the predictive value of r(m) estimates among moderately resistant accessions, we determined the increase in aphid numbers caged for 10 d after infestation of two 6-leaf plants per pot with 10 aphids per plant. Aphid counts were significantly higher on 'Toria-A' compared with UCD-13/1, UCD-310/3, and K-841; UCD-13/1 had significantly higher aphid counts than UCD-310/3, and K-841. When limited by host plant quality (damage), turnip aphid numbers on 'Toria-A' peaked on the 12th d; on UCD-13/1 and UCD-310/3 they peaked on the 18th d; and on K-841 on the 26th d after infestation. Overall, UCD-310/3 had the best antibiosis to L. erysimi of the accessions evaluated.