Intrinsic Rate of Increase (r_m) of <i>Aphis Gossypii</i> Glover Infesting Brinjal Plants

Abstract

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 F₁ generations. Similarly, the first progeny of F₁ generation were released in other glass chimneys to have F₂ generation. In this way, F₃, F₄ and F₅ 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 F₁ generation, followed by F₂ (0.317 ± 0.003) and it was lowest (0.303 ± 0.002) for F₅ 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