Thermal requirements of Tuta absoluta (Meyrick) and influence of temperature on its population growth on tomato.
The present study deals with the impact of temperature on development, survival, reproduction and population growth of a recently invaded and the most destructive pest of tomato, Tuta absoluta (Meyrick) with the aim to understand its possible expansion in different agro-climatic zones. Though T. absoluta was able to develop between 15° and 35°C, temperature around 25°-30°C was more suitable. Survival and fecundity were highest at 25°C and lowest at 35°C. Developmental threshold for different developmental stages of the pest varied from 6.2 to 9.5°C, while the thermal constant required by the insect to complete the development from egg to adult emergence was 500 degree-days. Population growth parameters were also influenced significantly by the rearing temperature. Intrinsic rate of increase, net reproductive rate and finite rate of increase was higher at 25° and 30°C as compared to other temperature regimes. The study concludes that T. absoluta can be a serious pest of tomato in mid-hills of north-western Himalayan region and the southern plains of India where temperatures varies between 15-35°C. Furthermore, the developmental threshold values indicate that the pest can develop and survive at temperatures as low as 6-9°C without entering the diapause as long as the food is available.