Demographic parameters of black aphid in cowpea cultivars.

The survival and development of Aphis craccivora Koch, 1854 (Hemiptera: Aphididae) can be affected by the characteristics of the different cowpea genotypes. The aim of this study was to estimate the demographic parameters of black aphid (Aphis craccivora Koch) in cowpea cultivars (Vigna unguiculata (L.) Walp.) of economic importance for Brazil. BRS Pingo de Ouro, BRS Tumucumaque, BRS Itaim, BRS Nova Era, BRS Imponente and BRS Guariba cultivars were used. VITA 7 cultivar articipated in the study as an insect susceptibility standard. A cohort was formed, where each cultivar had 10 plants as replicates, and each replicate received an aphid. The number of live individuals, the number of offspring, which were later removed and the longevity of the cohort insects were daily recorded. The finite growth rate (��) can be considered as the indicator parameter of outbreak risk for this pest if its values are above 1.2. BRS Nova Era, BRS Imponente, BRS Tumucumaque, VITA 7, BRS Itaim, BRS Pingo de Ouro and BRS Guariba cultivars presented �� values of 1.77, 1.74, 1.73, 1.73, 1.73, 1.71 and 1.16, respectively. For presenting survival on the occasion of the first offspring and gross reproduction rate (GRR), net reproduction rate (RO), RO / GRR ratio, intrinsic growth rate (rm) and finite growth rate (��) values much lower than the others, BRS Guariba cultivar is suggested to have antibiosis type resistance