Determination of thermal constant and developmental threshold of chilli thrips, Scirtothrips dorsalis Hood

Abstract

Temperature is one of most important abiotic factors that play an important role in population dynamics of insects. It directly influences the rate of development of insects. Experiment was conducted to assess the effect of temperature on rate of development of chilli thrips, Scirtothrips dorsalis Hood, an important sucking pest which causes serious loss to chilli crop. Rate of development of S. dorsalis was studied at three temperature regimes i.e.19± 1°C, 211 1°C, 25± 1°C, 29± 1°C, 32± 1°C and 35°C ± 1°C. A direct relationship between temperature and rate of growth of different life stages of S. dorsalis was observed. Whereas, an inverse association with developmental period of different life stages of S. dorsalis was found. The regression equation between temperature and development rate were developed for each stage of the insect. Thermal constant for egg, larva and pupa were determined as 147, 142.85 and 43.47 degree days (DD), respectively with corresponding developmental threshold being 16, 7.14 and 16.13°C. Accordingly 332 DD are required for S. dorsalis to complete one generation. The developed thermal constants will be useful in estimating S. dorsalis development and would help in timely action for effective management pest.