Estimation of Lower Developmental Threshold and Degree Days for Pupal Development of Different Geographical Populations of Chinese Citrus Fly (Diptera: Tephritidae) in China.

Abstract

The lower developmental threshold (LDT) and the number of developmental degree days (DDs) are fundamental parameters used to build phenology models that can be used to predict the timing of biological events during insect development. The Chinese citrus fly, Bactrocera minax (Enderlein) (Diptera: Tephritidae) is one of the most destructive citrus pest in China and Bhutan. This species overwinters as diapausing pupae in the soil before emerging as adults in the spring. In this study, B. minax collected from three representative geographical populations in China (Guizhou, Hubei, and Shaanxi) was used to conduct LDT experiments under laboratory conditions. Emergence data collected from pupae exposed to 10 constant temperatures was used to estimate the LDT and DDs required to complete pupal development for the three populations. The results show that LDT and DDs values for the Hubei and Shaanxi population are 11.9°C, 447.3 DDs and 11.5°C, 511.3 DDs, respectively. However, the geographic variation in pupal developmental rates was not statistically significant between the two populations. In addition, the Guizhou population was identified as a mixture of B. minax and B. tsuneonis (Miyake). The LDT and DDs values for the Hubei and Shaanxi populations obtained in this study can be used to predict adult emergence of naturally occurring field populations of B. minax within the majority of the citrus-growing production areas of China. These data can also be used in models to predict the risk of establishment of this species in the United States or other citrus-growing regions.