Effects Of Temperature And Humidity On The Growth, Development And Survivorship Of Galeruca Daurica (Joannis)

Galeruca daurica Joannis has become an increasingly serious pest of Allium spp. in the Inner Mongolia grasslands in recent years. Temperature and humidity are main environmental factors affecting the growth, development and survivorship of insects. We investigated the effects of temperature and humidity on the growth, development and survivorship of G. daurica in order to provide a scientific basis for forecasting this pest"s occurrence. The main results were summarized as follows:1. We determined the threshold temperature and the effective accumulated temperature oi G. daurica at five combinations of alternating temperatures (8/20 ℃, 11/23℃,14/26℃,17/29℃ and 20/32℃). The results showed that temperature affected significantly the developmental durations of various instar larvae and pupae, which shortened as the temperature increased under the condition of alternating temperatures. The developmental durations of 1st instar.2nd instar,3rd instar, overall larvae and pupae shortened from 11.00、13.44，23.18、46.42 and 16.89d at the lowest combination of alternating temperature (8’20℃. averaging 15℃) to 4.92、4.63、9.17、17.83 and 5.83d at the highest combination (20/32℃, averaging 27℃). The developmental threshold temperatures of 1 st instar.2nd instar.3rd instar. overall larvae and pupae were 5.04、8.84、 7.16、7.44℃ and 8.48℃, respectively, and the effective accumulated temperatures were 111.11、81.91、178.57、344.82 and 113.52 degree-days, respectively.2. We compared the effects of humidity on the egg hatchability and survival rates of larvae and pupae by use of the method of saturated aqueous salt solutions at a constant temperature of 20℃. The results showed that humidity affected significantly the egg hatchability and survival rates of larvae and pupae, and with the increasing humidity, the egg hatchability increased whereas the survival rates of larvae and pupae. Under the different humidity of 53.82%,83.77%、85.32% and 89.34%, the hatching rates of eggs are 69.60%、94.66%、93.76% and 98.65%, respectively, the survival rates of larvae are 60.00%、50.00%、56.67% and 31.67%, respectively, and the survival rate of G. daurica adults are 91.41%、72.01%、66.38% and 46.82%, respectively.