Biology and demographic growth parameters of cowpea aphid ( Aphis craccivora ) on faba bean ( Vicia faba ) cultivars

The performance of cowpea aphid, Aphis craccivora Koch. (Hemiptera: Aphididae), on five faba bean, Vicia faba L. (Fabales: Fabaceae) cultivars was evaluated. Colony development, biology, and demographic parameters were studied to measure the cowpea aphid performance. Two methods, whole plant and detached leaf, were used in these experiments. After 14 d , the number of apterous adult, nymphs, and total cowpea aphids were significantly lower in cultivar Gazira2 and highest on cultivar Misr1. Assuming that low aphid numbers per plant represented high resistance, the order of resistant cultivars was as follows: Gazira2 > Misr > Giza3 Improved > Goff1 > Misr1. Aphid infestation significantly inhibited plant growth compared with uninfested plants, as indicated by factorial analysis using plant height ( F = 41.38, P < 0.0001). The detached-leaf biological assay showed that the cultivar Gazira2 was less suitable than Misr1 because it had longer prereproductive, reproductive, and post reproductive periods, longer total longevity, and lower number of progeny. Similarly, demographic parameters also justified the suggested lower suitability of Gazira2 compared with Misr1, indicated by significantly lower net reproduction rate, intrinsic rate of increase, finite rate of increase, but longer generation time and doubling time on Gazira2. It was shown that cowpea aphid performed differently on the whole plant as compared with detached leaves. The detached-leaf biological assay is recommended for future experiments because it is more accurate and efficient and it produces reliable data.