Effect of temperature on the development of Echinothrips americanus Morgan (Thysanoptera: Thripidae) with special reference to the number of generations

The thrips Echinothrips americanus Morgan (Thysanoptera: Thripidae) was recently reported in China. The effect of temperature on its development was investigated and the potential area of further dispersal was predicted by estimation of its generations in China. First instar larvae developed to adults on green peppers Capsicum anuum at all constant temperatures (16, 19, 22, 25, 28, 31 and 34 degrees C) except for 34 degrees C, at which they developed only as far as the second instar. The percentage surviving of immature stages were not significantly different at the other six temperatures (range 32.10%-52.72%). The developmental times from egg to adult ranged from 11.68 to 45.13 days and were negatively correlated with temperature. There were significant differences between male and female immature stages in their developmental time at 22 degrees C and 25 degrees C. Regression analysis indicated that both the Lactin and linear models could describe the relationship between developmental rate and temperature for immature stages but a slightly higher coefficient of determination was obtained with the Lactin model. The high-temperature threshold and the optimum temperature for development were 32.04 degrees C and 31.79 degrees C, respectively, estimated by the Lactin model. The low -temperature threshold for development was 11.35 degrees C and thermal constant was 229.76 degree-days for immature stages, estimated by the linear model. The models predicted that E. americanus could have produced 8-10 generations per year under field conditions in Beijing (N39 degrees 56', E116 degrees 17') and Yangling (N34 degrees 12', E108 degrees 7') from 2002 to 2012. The potential risk posed by E. americanus to crops in different regions of China was discussed.