Effects of Constant Temperature Regimes on the Life Table Parameters of Plutella xylostella (Lepidoptera: Plutellidae) (Linnaeus)

Abstract

The study was conducted to determine the effect of different temperatures (24 °C, 28 °C, and 32 °C) on the life table of Plutella xylostella (Lepidoptera: Plutellidae) (Linn.) under the laboratory conditions (65 ± 5% relative humidity and 14 L: 10 D photoperiod). The findings revealed that the age-specific, stage-specific, and female fertility life table was significantly influenced by temperatures. The highest temperature (32 °C) decreased the life cycle duration and life expectancy of P. xylostella, while the lowest (24 °C) increased both. The survival time of immature stages decreased linearly with increasing temperature between 24 °C and 32 °C. The maximum survival rate and lowest mortality were found at 28 °C, followed by 24 °C and 32 °C, respectively. The mortality was recorded highest in the egg and pupal stages at 32 °C and 24 °C. While within the larval stage, the maximum mortality was recorded at 1st instar (14) at 24 °C and 32 °C and 3rd instar (12) at 28 °C. However, the maximum generation mortality was found at 32 °C (0.66), followed by 24 °C (0.57) and 28 °C (0.48), respectively. The potential fecundity (Pf) and net reproductive rate (Ro) were highest at 28 °C (316.18 and 70.54 females/female/generation) and lowest at 32 °C (253.03 and 40.34 females/female/generation), while a moderate value was observed at 24 °C (294.06 and 58.84 females/female/generation). Both mean and corrected generation time (Tc and τ) were shortest for 32 °C (20.14 and 19.43 days) and longest for 24 °C (29.93 and 28.77 days). The population of P. xylostella was double with a minimum time duration at 32 °C (3.77 days) and a maximum at 24 °C (5.09 days). The maximum monthly rate increase was found at 32 °C and the minimum at 24 °C, while the medium was at 28 °C. Based on experimental findings, we conclude that the 28 °C temperature was favourable for the growth and development of P. xylostella.