Study on the mortality of the stored-grain insects adults in different concentrations of low oxygen

During this research, adults of Liposcelis bostrychophila Badonnel, Oryzaephilus surinamensis (Linnaeus), Tribolium confusum Jacquelin du Val, two strains of Tribolium castaneum (Herbst) (from Zhongshan and Yiyang), Sitophilus oryzae (Linnaeus) and Sitophilus zeamais Motschulsky were first kept in various low oxygen atmospheres whose concentrations were 0%, 1% and 2% for different exposure times, then in the normal atmosphere. The data and trend of mortality changes accompanied by the low oxygen concentration and exposure time were gained after this research. Results indicate that there were obvious inter-specific differences among the test insects in the sensitivity to low oxygen atmosphere, and the sensitivity declined as follows: L. bostrychophila, O. surinamensis, T. confusum, T. castaneum, S. oryzae and S. zeamais. The insects of closely related species presented diverse responses to the low oxygen stress. Tribolium confusum and T. castaneum showed a very dissimilar sensitivity to the low oxygen atmosphere, but there was no obvious difference between S. oryzae and S. zeamais. A fast lethal effect on the adults of L. bostrychophila, O. surinamensis, T. confusum and T. castaneum was observed when exposed to 0% oxygen. At 1% and 2% oxygen atmosphere, the mortality level of T. castaneum exceeded 60% and 80%, respectively. The lethal effect of 2% was more efficient than 1% oxygen, which was the same as S. oryzae and S. zeamais at 2% oxygen atmospheres. The mortality of S. oryzae and S. zeamais at 1% and 2% oxygen concentration was higher than at 0%, and the mortality of these two insects might be higher under the condition of a small amount of oxygen. At 1% and 2% oxygen atmosphere, the growth trend of the cumulative mortality of T. confusum and T. castaneum generally conformed to the classical model of the logistic formula which indicated the response of insect pests when applying common insecticide. These results are useful to extend the control technology of stored-grain insects with low oxygen universally.Keywords: Low oxygen; Stored-grain insect; Mortality; Treatment duratio