Developmental threshold and degree-day requirements of the Onion thrips, Thrips tabaci Lindeman in laboratory condition

An experiment was designed to determine the lower thermal threshold, and degree-days requirements of onion thrips, Thrips tabaci Lindeman. Developmental time of the insects, collected from cotton fields in Kashmar-Iran, was recorded at four different temperatures with 60-70% RH and a photoperiod of 16: 8 (L: D) h. The life cycle from egg to adult emergence lasted 27.1, 21.0, 15.3 and 11.3 days at 20, 23.5, 26 and 34 °C, respectively. Shortest developmental time was observed at 34 °C. Development time increased linearly with the decrease of temperature. The longest development time was observed in the larval stage about 41% of the total developmental time. Similarly, the developmental time percentages for egg, pupae and prepupae stages was 28, 18 and 13, respectively. The highest rate of development was observed in prepupae stage, was found to be the most temperature sensitive. The developmental times for egg, larvae, prepupae and pupae were 4.3, 5.6, 2.0 and 3.4 days, respectively at 26°C. Lower thermal threshold of the insect was 9.89C, and degree-days for one generation was 269.6.