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Abstract
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Temperature-dependent life table studies were performed to evaluate the direct effects of rising temperatures (20, 22.5, 25, 30, 35, 37.5 and 40 °C ± 0.5) on Helicoverpa armigera (Hübner) (Lep: Noctuidae). The obtained results indicated that H. armigera could successfully survive and reproduce at all temperatures tested except at 37.5 and 40 °C (at 37.5 °C, no adults emerged, and at 40 °C, no eggs hatched). However, a significant difference was observed among mean life table parameters of H. armigera at survived temperatures. The constant temperatures of 22.5 and 25 °C were considered as the optimum degree of eggs laid by female of H. armigera. The intrinsic rate of increase (r) at the above-mentioned temperatures varied from 0.080 day−1 at 35 °C to 0.145 day−1 at 22.5 °C. In addition, the value of the net reproductive rate (R0) of H. armigera at the different temperatures tested varied from 9.22 offspring at 35 °C to 501.01 offspring at 22.5 °C. Furthermore, the values of the gross reproductive rate (GRR) were significantly different at the tested temperatures, and the lowest and highest values of this parameter were obtained at 35 °C (42.18 offspring) and 22.5 °C (1056.44 offspring), respectively. Immature mortality increased with increasing temperature. The results obtained in the present study may provide insight to predicting population dynamics and the efficacy of the subsequent management programs of this pest.
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