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Abstract

Temperature-dependent development and demography of Zygogramma bicolorata (Coleoptera: Chrysomelidae) on Parthenium hysterophorus.

Abstract

Development of Zygogramma bicolorata (Coleoptera: Chrysomelidae), was evaluated at 10°C, 15°C, 20°C, 25°C, 27°C, 30°C, 32°C, 35°C and 38°C with 65% RH and 10L:14D h on Parthenium hysterophorus. Development of immature was significantly (P<0.05) prolonged to 63.65-days at 15°C compared to 24.85-days at 35°C, while development was not recorded at 10°C and 38°C. For immature development, values of lower temperature threshold (Tmin) and thermal constant (K) were 4.31°C and 769.23 degree-day (DD), respectively, in linear model. Optimum temperature (Topt) for immature development was estimated to be 21.60°C with the help of cubic polynomial non-linear equation. Furthermore, other models were also evaluated to check the accuracy of estimated thresholds and biological values of integral coefficients. Consequently, non-linear model was accepted and recommended for description of thermal-based development of Z. bicolorata. Among the non-linear models Briere-2 model was found suitable for determination of developmental rate as Topt and Tmax with acceptable value of 27.19°C and 30.39°C, respectively. Demographic parameters were also studied at tested temperatures. Potential fecundity (Pf), intrinsic rate of increase (rm) and finite rate of increase (λ) were highest, however mean generation time (Tc) and doubling time (DT) were lowest at 27°C and 30°C, respectively. Kaplan-Meier (K-M) estimation showed an inversely proportional relationship between female survivorship and temperatures. Female biased sex ratio was evident at all constant temperatures tested. Thus, it can be concluded that development of immature of Z. bicolorata was decreased with increase of temperature and optimum development occurred at 27°C and 30°C. Moreover, life table parameters of Z. bicolorata can be used to develop the models of population dynamics and prediction.