The Impact of Temperature on life-history traits of the bird cherry-oat aphid, Rhopalosiphum padi (Hemiptera: Aphididae) reared on wheat seedlings

Abstract

The impact of temperature and some life table parameters of Rhopalosiphum padi (Linnaeus, 1758), were investigated at 18, 20, 22 and 24°C constant temperatures. The development durations decreased as the temperature increased, recorded 8.36, 7.65, 6.8 and 5.19 days at 18, 20, 22 and 24°C, respectively. The temperature threshold for the development of first, second, third and fourth instars and overall nymphal stage were 4.53, 7.96, 10.02, 9.67 and 8.25°C, respectively. The thermal units required for each nymphal instar; first, second, third and fourth and overall nymphal stages were 27.78, 21.28, 16.39, 22.22 and 83.33 day-degrees, respectively. The average adult fecundity was as high as 91.74 and 73.25 offspring at 20 and 22°C, but dropped to 47.66 and 63.45 offspring at 18 and 24°C. However, the average (mx) values per female/day were 2.24, 2.12, 1.93 and 1.01 offspring at 20, 24, 22 and 18°C, respectively. The highest net reproduction rates (R0) were 61.46 and 54.42 at 20 and 22°C, and mean generation time (T) and population doubling time (DT) diminished as temperature increased. The intrinsic rate of increase (rm= 0.3 and 0.25) and the finite rate of increase (λ= 1.36 and 1.29 nymphs/female/day) were greatest at 24 and 22°C, respectively. The results indicated clearly that temperatures from 20 to 24°C were in the favourable range for survival and reproduction of this serious pest.