Carbon dioxide improves ethanedinitrile efficacy for fumigating the stored product pests Rhyzopertha dominica and Lasioderma serricorne

The toxicity of ethanedinitrile (EDN), an alternative fumigant for stored products, is decreased due to the high sorption of the gas in treated commodities. This laboratory study examined adding carbon dioxide to EDN to increase activity against Rhyzopertha dominica and Lasioderma serricorne at 25 °C, 50–70% R.H and a photoperiod of 16 L:8D h for 24 h. CO2 at 30% with the estimated LC25 dose of EDN exhibited a significant effect on the mortality of adults of R. dominica and the larvae, pupae, and adults of L. serricorne. Adults emerged from the mixed life stage cultures of R. dominica exposed to a mixture of 75 ppm or 150 ppm of EDN and CO2 at 10, 20 and 30% averaged 26.8, 11.5 and 4.9, and 1.5, 0.6 and 0.9, respectively. Averages of 188.6 and 56.6 adults resulted from cultures of R. dominica fumigated with EDN at 75 and 150 ppm alone, respectively. The L. serricorne cultures exposed to EDN at 500 or 1000 ppm plus 10, 20, and 30% of CO2 yielded average numbers of emerged adults of 170.5, 110.9 and 114.6, and 68.3, 30.2 and 31.9, respectively, compared to 358.3 and 173.6 in cultures treated with 500 and 1000 ppm of EDN alone, respectively. Numbers of adults of both species emerged from cultures exposed to either EDN or CO2 alone in the presence of commodities were significantly higher than those exposed to the EDN + CO2 (30%) mixture. These results clearly indicated the positive effect of CO2 on toxicity of EDN that can overcome the decrease of EDN toxicity against the treated insects due to its sorption in commodities.