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

Abstract The cowpea aphid Aphis craccivora is a polyphagous species that has spread worldwide. The aim of this study was to investigate the thermal effects on the developmental period, longevity, and fecundity of apterous females of A. craccivora. The experiment was conducted under the effects of four temperature regimes, which included 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. Afterwards, the nymphs developed successfully until the adult stage at all temperature regimens. The developmental period of immature A. craccivora ranged from 10.6 days at 16°C to 5.0 days at 28°C. The nymph viability and survival were greater at 24°C than at the other temperatures. However, at a constant temperature of 28°C, the mortality rate was greater than that of the other species at the immature stage of A. craccivora. The lower developmental threshold for cowpea aphids was estimated at 1.77°C and 66.79 degree-days (DD) at the first instar until adulthood. 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, and the smallest occurred at 16°C (rm= 0.177). It was obvious that temperatures greater than 28°C resulted in good development, increased mortality at the nymphal stage, reduced adult longevity, and diminished fecundity. The optimal growth temperature for A. craccivora was 20°C-24°C.