Demographic attributes of the parthenium beetle Zygogramma bicolorata (Coleoptera: Chrysomelidae) under different variables

Abstract

The demographic attributes of the parthenium beetle Zygogramma bicolorata Pallister were studied using Parthenium hysterophorus L. as food under different abiotic and biotic variables. Intrinsic and finite rates of increase were highest with the shortest mean generation and doubling times when Z. bicolorata was fed on inflorescences followed by the leaves and stems of P. hysterophorus. Temperature significantly affected the demographic parameters. The net reproductive rate was highest at 27 8C and lowest at 35 8C. Different photoperiodic exposures altered the demographic attributes of the beetles with long-day exposure (14L:10D) resulting in optimal values compared with other photoperiodic exposures. Continuous darkness (0L:24D) and continuous light (24L:0D) suboptimally affected the demographic attributes of the beetles. In response to the light of different wavelengths, the net reproductive rate, and intrinsic and finite rates of increase were significantly higher when the beetles were reared under a broad spectrum of white light followed by those under , 570 nm (yellow), , 475 nm (blue) and , 650 nm (red). Information gained in this study may be helpful in the mass multiplication of Z. bicolorata, and thereby strengthening the biocontrol of parthenium weed.