Effects of temperature on development of the azuki bean weevil,Callosobruchus chinensis (Coleoptera: Bruchidae) on two leguminous seeds

The azuki bean weevil, Callosobruchus chinensis L., is one of the most serious stored product pests in the world. The temperature driven stage-specific development of C. chinensis was examined at eight constant temperatures of 15.97, 18.31, 22.09, 26.15, 30.50, 34.39, 38.00, and 40.00 °C on azuki bean (Vigna angularis [Wild.] Ohwi & Ohashi) and cowpea (Vigna unguiculata L.) seeds. Parameters for stage-specific development such as threshold temperatures and thermal constants were determined by linear and nonlinear models. The total developmental time (egg - adult) decreased with increasing temperature from 14 to 38 °C on both seeds. However, total developmental time varied from 127.93 to 122.25 days at 15.97 °C to 19.31 and 19.17 days at 38.00 °C on azuki bean and cowpea seeds, respectively. The nonlinear Logan-6 and Performance models estimated optimal temperatures as 37.3, 37.0, 36.5 and 37.1 °C on azuki bean, and as 36.7, 36.4, 34.5 and 36.6 °C on cowpea for egg, larva, pupa and egg to adult, respectively. The linear model estimated the lower temperature thresholds (T_min) of egg, larva, pupa and egg to adult as 16.97, 10.47, 1.36, and 10.28 °C on azuki bean, respectively, and 16.84, 10.33, 10.92, and 9.83 °C on cowpea, respectively. The thermal constants (K) for each stage completion was 35.13, 255.21, 233.11, and 503.41° days (DD) for egg, larva, pupa, and egg to adult on azuki bean, respectively and 32.45, 246.50, 107.04, and 490.02 DD for egg, larva, pupa, and egg to adult on cowpea, respectively. Temperature also influenced the adult longevity. These findings on thermal requirements and temperature thresholds can be used to predict the occurrence, number of generations and population dynamics of C. chinensis.