Effect of temperature on the biological parameters of the cabbage aphid Brevicoryne brassicae

The cabbage aphid, Brevicoryne brassicae, is a pest of many plants of the Brassicaceae family including cabbage, Brassica oleracea Linnaeus, 1753. We investigated the effect of temperature on the biological parameters of B. brassicae using different temperature-based models incorporated in the Insect Life Cycle Modelling (ILCYM) software. Nymphs of first stage were individually placed in the incubators successively set at 10 degrees C, 15 degrees C, 20 degrees C, 25 degrees C, 30 degrees C, and 35 degrees C; 75 +/- 5% RH; and L12: D12-hr photoperiods. We found that first nymph reached the adult stage after 18.45 +/- 0.04 days (10 degrees C), 10.37 +/- 0.26 days (15 degrees C), 6.42 +/- 0.07 days (20 degrees C), 5.076 +/- 0.09 days (25 degrees C), and 5.05 +/- 0.10 days (30 degrees C), and failed at 35 degrees C. The lower lethal temperatures for B. brassicae were 1.64 degrees C, 1.57 degrees C, 1.56 degrees C, and 1.62 degrees C with a thermal constant for development of 0.88, 0.87, and 0.08, 0.79 degree/day for nymphs I, II, III, and IV, respectively. The temperatures 10, 30, and 35 degrees C were more lethal than 15, 20, and 25 degrees C. Longevity was highest at 10 degrees C (35.07 +/- 1.38 days). Fertility was nil at 30 degrees C and highest at 20 degrees C (46.36 +/- 1.73 nymphs/female). The stochastic simulation of the models obtained from the precedent biological parameters revealed that the life table parameters of B. brassicae were affected by the temperature. The net reproduction rate was highest at 20 degrees C and lowest at 30 degrees C. The average generation time decreased from 36.85 +/- 1.5 days (15 degrees C) to 6.86 +/- 0.1 days (30 degrees C); the intrinsic rate of increase and the finite rate of increase were highest at 25 degrees C. In general, the life cycle data and mathematical functions obtained in this study clearly illustrate the effect of temperature on the biology of B. brassicae. This knowledge will contribute to predicting the changes that may occur in a population of B. Brassiace in response to temperature variation.