Thermal effects on the biological parameters of Aphis craccivora (Hemiptera: Aphididae) on bean

Abstract The cowpea aphid, Aphis craccivora is a polyphagous specie that has spread all over the world. The aim of this study was to investigate the thermal effects on the developmental period times, longevity, and fecundity of apterous females of A. craccivora. The experiment was conducted under the effects of four temperature regimes, which are 16°C, 20°C, 24°C, and 28°C, with 65 ± 5% relative humidity (RH) and a photoperiod of long-day 16:8 (L:D) h. After transferring the nymphs developed successfully until the adult stage at all temperature regimes. The developmental periods of the immature A. craccivora ranged from 10.6 days at 16°C to 5.0 days at 28°C. The nymph viability and survival were longer at 24°C than the others. However, at the constant temperature of 28°C, the death ratio was higher than others at the immature stages of A. craccivora. The lower developmental threshold for cowpea aphid was estimated at 1.77°C and 66.79 degree-days (DD) at the first instar until adult. The average longevity of adult females decreased from 22.2 days at 16°C to 10.8 days at 28°C. The net reproduction rate per female was 46.97 at 24°C and 26.93 to 28°C. The largest intrinsic rates of increase (rm= 0.367) occurred at 28°C, the smallest at 16°C (rm= 0.177). It was obvious that temperatures over 28°C provided a good development, increased-mortality at the nymphal stages, reduced adult longevity, and diminished fecundity. The optimal growth variation of A. craccivora on beans was 20°C-24°C.