Effects of temperature and relative humidity on the life table of phenacoccus solenopsis tinsley (hemiptera: Pseudococcidae) on cotton

Abstract

Phenacoccus solenopsis, the cotton mealy bug, has emerged as a serious pest of cotton in India, necessitating basic studies on its development and survival at different temperatures (20, 25, 30 and 35 °C) and relative humidities (RH) (65, 75 and 85 ± 1 %) levels to ascertain optimal population growth. A life table was constructed using temperature and humidity. The nymphal duration was 20.2 d at 35 ± 1 °C and 65 ± 1% RH, but lengthened to 26.6 days at 20 ± 1 °C and both RH combinations. Adult longevity was 16.4 days at 20 ± 1° C and 65% RH, but 10.8 days at 35 °C at the same RH; however it was 6.4 days at a temperature of 20 ± 1 °C and 75% RH. Fecundity was at its maximum (489 nymphs/female) at 35 ± 1 °C and 65% RH, with lower fecundity at 75% RH across all temperature levels. The net reproductive rate (Ro) and finite rate of increase () were 141.3 females/female/generation and 1.24 fold per female per day, respectively at 35 ± 1 °C and 65% RH suggesting that the population would increase more than 140 times per generation and 1.24 times per female per day. The rates of increase at higher relative humidities were generally lower than at 65% RH. Nymphs failed to complete development at 85% RH at all temperature levels. The intrinsic rate of increase (rm) was the highest (0.215) at 35 °C in combination with 65% RH. Our results suggest that 35 ± 1°C and 65% RH is the most favorable temperature and RH combination for the optimal population growth of the Punjab strain of P. solenopsis. Our study also predicts the expansion of this pest to other parts of the world in which the average temperature equals to 35 °C with 65% RH.