Sawai, Dr. H. R.PEDDU, HEMANT VENKTESHWARA PRASAD.2021-05-302021-05-302019-07-22PEDDU, HEMANT VENKTESHWARA PRASAD. (2019). Estimation of developmental thresholds and thermal requirements for cotton pink bollworm, Pectinophora gossypiella (Saunders). Department ofagricultural entomology, Nagpur. Dr. Panjabrao Deshmukh Krishi Vidyapeeth, Akola. M. Sc. 2019. Print. xiii, 103p. (unpublished).https://krishikosh.egranth.ac.in/handle/1/5810169400It relates to crucially deepen the knowledge base and help in comprehending seasonal dynamics of P. gossypiella in the context of climate change, which could further facilitate in undertaking agro-ecoregion specific management strategies.The pink bollworm, Pectinophora gossypiella (Saunders) is one of the most damaging insectpests of cotton, worldwide. The recent re-emergence of pink bollwormon Bt cotton in central and south cotton growing zones of India posed a serious challenge to the cotton production of the country. With predicted climatic changes, the pest status of pink bollworm is likely to be aggravated. In this context, a detailed knowledge of temperature-dependent population growth potential of pink bollworm is of paramount importance to undertake timely management actions before the pest could inflict much damage to the crop. In present study, a temperature-dependent population growth potential of pink bollworm was studied by rearing it on detached green bolls of cotton (~10 day old) at six different constant temperatures (15⁰C - 38⁰C) in laboratory. Several linear and non-linear models of biological significance to the development of poikilothermic organismswere fitted to the data on each life stage, e.g. cumulative logit distribution function (development time), Sharpe and DeMichele model (Development rate), Wang model (mortality), Stinner model (adult longevity), Gaussian with log function (total fecundity) and exponential modified function (age-related oviposition rate). Based on the established functions, the thermal thresholds, thermal unit requirements and temperature-dependent population growth potential of pink bollworm were estimated. Using stochastic simulation centered on cohort updating and rate summation approach, the life table parameters of pink bollworm at different constant temperatures were simulated. All the analyses were carried out using Insect Life Cycle Modeling (ILCYM) software, Version 3.0, developed by International Potato Center, Lima, Peru. The results revealed that the temperature-dependent rate of development for all the immature life stages of pink bollworm increased linearly until approximately 34°C-35°C, after which it became non-linear and declined abruptly. The theoretical lower developmentthreshold temperatures estimated using linear regressions for immature life stages of pink bollworm applied to mean development rateswere 11.23⁰C, 11.37⁰C, 11.00⁰C and 11.20°C for egg, larvae, pupae and mean threshold for egg-pupae, respectively. The thermal unit requirements for development of different life stages of pink bollworm obtained using inverse of the slope of the regression equation were 72.99 DD, 285.71 DD, 144.92 DD and 503.62 DD for eggs, larvae, pupae and cumulative DD for egg-pupae, respectively. The extreme temperature of 38°C was found lethal to egg and larval stages of pink bollworm at which no development to the next stage occurred. Both the female and the male adults of pink bollworm had an optimal lifespan at temperatures between 20°C and 35°C. The females laid very few eggs at 15°C temperature, and no egg laying occurred at 38°C temperature. This demonstrates the importance of prevailing temperatures in determining the climatic suitability for mating and reproduction in pink bollworm.The life table parameters estimated at different constant temperatures indicated that the pink bollworm population could grow at temperatures between 20⁰C-35⁰C, however themostfavoured range of temperature for its optimum growth was observed between 25⁰C -30⁰C. The maximum net reproductive rate of 16.302 females/ female/ generation and highest total fecundity of 56.565 individuals/ female/ generation were obtained at 25⁰C temperature. Mean length of generations decreased from 63.183 days at 20⁰C to 31.673 days at 30⁰C. The maximum finite rate of increase (1.059 - 1.064 females/ female/ day) and shortest doubling time (11.228 – 12.278 days) were observed at temperatures between 25⁰C and 30⁰C. All the estimated developmental functions and life table parameters of pink bollworm at constant temperatures between 15-38⁰C were reasonably similar when compared with literature reports. The outputs of the present study will be helpful in understanding and comprehending seasonal dynamics of pink bollworm under varied temperature conditions, which could facilitate in undertaking agro-ecoregion specific management strategies for this pest in the context of climate change.EnglishCrop protection, Pests.Thesis