Efficacy of atmospheric and pressurized carbon dioxide or air against Sitophilus zeamais Motchulsky (Coleoptera: Curculionidae) and Tribolium castaneum (Herbst) (Coleoptera: Tenebrionidae) in milled rice

Abstract

Carbon dioxide gas was evaluated in the laboratory for control of Sitophilus zeamais Motchulsky and Tribolium castaneum (Herbst) in milled rice using a specially designed pressure chamber. Tests were conducted at atmospheric pressure with 60, 80 and 100% carbon dioxide and with 100% carbon dioxide pressurized to 4, 6 and 8bars. LT99 were ≤79, ≤78, and ≤148h for all life stages of S.zeamais exposed to 60, 80 and 100% carbon dioxide, whereas, they were ≤59, ≤51 and ≤66h for T.castaneum. Pure carbon dioxide controlled the adult stage, but there tended to be no significant differences of carbon dioxide concentrations on mortality of immature stages. When pure carbon dioxide was pressurized, mortalities of the two insect species were increased significantly. LT99 values decreased with levels of applied pressure: ≤29, ≤9.0 and ≤4.8h for S.zeamais and ≤15, ≤5.8 and ≤2.3h for T.castaneum at pressures of 4,6 and 8bars, respectively. Sitophilus zeamais was more tolerant than T.castaneum to carbon dioxide gas. The adult was the most susceptible stage, however, immature stages responded differently to carbon dioxide gas applied at varying concentrations and pressure levels. Adult mortalities were lower when air was used in the pressure chamber instead of carbon dioxide. Pressurized carbon dioxide at relatively low pressure (4-8bars) was found effective in controlling all live stages of S.zeamais and T.castaneum in milled rice with shorter exposure times than at atmospheric pressure using an inexpensive set of equipment as compared to high pressure carbon dioxide fumigation (20-30bars). © 2013 Elsevier Ltd.