Cotton aphids, Aphis gossypii Glover (Homoptera: Aphididae), obtained from cotton, Gossypium hirsutum L., fields in the Gorgan region of northern Iran, were colonized on ‘Varamin’ cotton plants in a growth chamber. The development, survivorship, and life table parameters of the cotton aphid were evaluated at 27.5 ± 1°C, 65 ± 10% RH, and a photoperiod of 14:10 (L:D) h of artificial light on five commonly growing cotton cultivars: Varamin, ‘Sealand’ (relatively resistant cultivar), ‘Bakhtegan’, ‘Sahel’ (both relatively susceptible cultivars), and ‘Siokra’ [resistant to Bemisia tabaci (Gennadius)]. The developmental times of immature stages ranged from 4.6 d on Bakhtegan and Varamin to 6.3 d on Sealand ,whereas the immature survival was 97.5 to 65% on Sahel and Siokra, respectively. On average, there were 28.7, 28.3, 23.5, 20.1, and 16.8 nymphs produced per female on Sahel, Bakhtegan, Varamin, Sealand, and Siokra, respectively. The intrinsic rate of natural increase (rm) for cotton aphids on Sahel was the highest, whereas the values for rm varied from 0.284 (nymphs per female per d) on Siokra to 0.368 on Sahel. Jackknife estimates of generation times (T), net reproductive rate (R0), doubling time (DT), and finite rate of increase (λ) on these cultivars were as follows: 9.79–10.84 d for T, 9.23–23.81 nymphs per female for R0, 2.17–3.19 d for DT, and 1.28–1.38 nymphs per female per d for λ. Cotton aphid performance was at its highest on Sahel and lowest on Siokra.
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Vol. 99 • No. 5