Threshold temperature and heat unit requirements for the development of the granary weevil,Sitophilus granarius(L.)

The objective of the present investigation was to determine the effects of temperature on the granary weevil, Sitophilus granarius L., in the laboratory so that forecasting models based on heat accumulation units could be developed for the pest. Development of S. granarius reared on wheat grains was studied at three constant temperatures (15, 20 and 25 °C) and relative humidity of 70 ± 5%. The developmental time was significantly decreased with the increase in temperature. The developmental threshold temperatures estimated for egg, larva, pupa and from egg to adult were 7.79, 7.31, 14.08 and 9.97 °C, respectively. Based on these thresholds, the developmental stages, respectively, needed 92.75, 393.78, 45.04 and 562.36 day degrees to complete their development. Also, about nine generations were calculated for the pest per year under Assiut prevailing conditions. It seems that temperature of 25 °C is the most favourable developmental temperature.