Intrinsic Rate of Increase (r m ) of Aphis Gossypii Glover Infesting Brinjal Plants

Context: Intrinsic rate of natural increase (r m ) of Aphis gossypii is important factor to know the actual increase of population which is governed by physical factors of environment. Objectives: The aims of this study were to determine the intrinsic rate of natural increase (r m ) of A. gossypii which is the basic knowledge of IPM program. Materials and Methods: The nymphal duration, pre-reproductive period, reproductive period, fecundity, longevity, etc. were observed within the glass chimneys. The newly born nymphs were considered as F 1 generations. Similarly, the first progeny of F 1 generation were released in other glass chimneys to have F 2 generation. In this way, F 3 , F 4 and F 5 generations were obtained. Data for duration between birth of a nymph and its first laid progeny (d) and number of progeny (M d ) per female were recorded. Altogether data of 8 replications were considered for the calculation of intrinsic rate of natural increase (r m ) of A. gossypii infesting brinjal plants. Results: Intrinsic rate of natural increase (r m ) value was highest (0.322 ± 0.005) for the F 1 generation, followed by F 2 (0.317 ± 0.003) and it was lowest (0.303 ± 0.002) for F 5 generation. Temperature influenced the (r m ) significantly (r= 0.903, p<0.05). Dew point also influenced the r m of A. gossypii significantly (0.882 P<0.05). Relative humidity played insignificant role (r= 0.428) on the r m of A. gossypii. Conclusion: The results obtained in this study are essential to know the actual populations increase which important to pest control. Key words: Aphis gossypii ; brinjal; intrinsic rate of increase. DOI: 10.3329/jbs.v17i0.7118 J. bio-sci. 17: 123-127, 2009