Efficacy of vaporised ethyl formate/carbon dioxide formulation against stored‐grain insects: effect of fumigant concentration, exposure time and two grain temperatures

BACKGROUND: The ethyl formate/carbon dioxide (CO(2)) formulation Vapormate is a rapid-acting fumigant being developed for the control of stored-grain insects. The effects have been investigated of concentration, exposure times of 1, 3, 24 and 72 h and two grain temperatures, 15 and 25 degrees C, on its efficacy against mixed-stage cultures of Sitophilus oryzae (L.) Tribolium castaneum (Herbst) and strongly phosphine-resistant Rhyzopertha dominica (F.) strain QRD569. RESULTS: High mortalities (> or = 92%) of mixed-stage cultures of all three species were obtained when grain was fumigated with the formulation (193 g m(-3) ethyl formate) for 1 h. Complete control of R. dominica QRD569 and T. castaneum was achieved with 63 and 76 g m(-3) ethyl formate respectively, with exposure for 24 h, whereas mean mortality of S. oryzae was 86% under the same conditions. Mortalities of S. oryzae juvenile stages were significantly lower than adults under the conditions tested, which was due to pronounced tolerance of mid-stage pupae to the fumigant. Reducing grain temperature from 25 to 15 degrees C had no effect on insect mortality. CONCLUSION: Ethyl formate/CO(2) formulation is highly effective against stored-grain insects over a range of concentrations and exposure times. Efficacious fumigations were conducted in as little as 1 h, and a strongly phosphine-resistant R. dominica strain was readily controlled with the fumigant.