Life Table and Population Parameters ofNasonovia ribisnigri(Homoptera: Aphididae) at Different Constant Temperatures

Abstract

Age-specific life tables of the lettuce aphid, Nasonovia ribisnigri (Mosley), feeding on lettuce were determined at different constant temperatures under controlled conditions. Our results showed that the proportion of alates increased with increasing temperatures, remaining below 7% at 16°C and increasing to 40–57% at a temperature above 20°C. The longest developmental time of apterous aphids was obtained at 8°C (31.5 d), and the shortest was at 26°C (6.2 d), whereas the developmental time of alates was always 0.7–1.1 d longer than for apterous. Most aphids needed four instars to reach adult stage, but at 8, 26, and 28°C, many individuals passed through five or six molts. Age-specific survivorship (lx) was always above 90% at the temperature range of 16–24°C. Mortality rate (qx) was rather low but constant at 8°C. However, mortality was high at 28°C and occurred mainly in the last nymphal instars and adult stage. Unexpectedly, no nymphs were produced by the adult morphs at 28°C, but effective fecundity was high at 8°C. Fecundity for alates was always lower than for the apterous aphids at the same temperature. The largest intrinsic rate of natural increase (rm), and the mean relative growth rate (⁠|$\rm\overline{RGR}$|⁠) occurred at 24°C, for both apterous and alate morphs, and the lowest at 8°C. Our results show that lettuce aphid is better adapted to survive and reproduce at low (8°C) than at high (28°C) temperatures, and its best performance occurred at 20–24°C.