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 (CO₂) 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 °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 (≥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 °C had no effect on insect mortality. CONCLUSION: Ethyl formate/CO₂ 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. Copyright © 2009 CSIRO, Australia. Published by John Wiley & Sons, Ltd     

甲酸乙酯对面粉中赤拟谷盗的熏蒸效果

本文研究了甲酸乙酯对面粉中赤拟谷盗不同虫态的熏蒸作用。通过对熏蒸期间熏蒸剂浓度检测,计算浓度时间乘积(CT)计算不同时间下甲酸乙酯对赤拟谷盗各虫态达到99%控制的处理指标(Lct_(99))。结果表明甲酸乙酯熏蒸能有效防治面粉中的赤拟谷盗各虫态,赤拟谷盗不同虫态对甲酸乙酯的敏感性由强到弱依次为:卵>低龄幼虫>成虫>高龄幼虫>蛹。在23℃条件下处理6h和12h对面粉中赤拟谷盗的Lct_(99)分别为448.42和599.34mg·h/L     

Field evaluation of vaporised ethyl formate and carbon dioxide for fumigation of stored wheat

BACKGROUND: Vapormate? is a cylinderised non‐flammable mixture of ethyl formate (16.7% by weight) and carbon dioxide (CO₂) that has been developed as a rapid fumigant of stored grain. Four field trials were undertaken on wheat in 50 t farm silos to demonstrate the feasibility of dynamic application. To assess treatment efficacy, each trial tested mixed stages of Rhyzopertha dominica F. (>11 000), Tribolium castaneum (Herbst.) (>1500) and Sitophilus oryzae (L.) (>13 000) in mesh cages positioned through the centre of the grain bulk and on the grain surface. Ethyl formate and CO₂ concentrations were measured in the silo during fumigation and in ambient air outside the 6 m fumigation zone. Application rates of 420, 660 and 940 g m^?3 of ethyl formate/CO₂ formulation and exposure times of 24, 3 and 72 h, respectively, were examined using wheat of 10.4–11.7% moisture content and grain temperatures between 2 and 32 °C. RESULTS: All life stages of R. dominica and T. castaneum were fully controlled under all conditions tested, and mortality of all life stages of S. oryzae was greater than 98%. CONCLUSION: Dynamic application of vaporised ethyl formate and CO₂ to 50 t silos proved safe to operators and rapidly effective against stored‐grain insects on cold to warm grain. Copyright © 2009 CSIRO, Australia. Published by John Wiley & Sons, Ltd     

甲酸乙酯对米象乙酰胆碱酯酶和羧酸酯酶的影响

报道了甲酸乙酯对米象[Sitophilus oryzae(Linnaeus)]乙酰胆碱酯酶(AChE)和羧酸酯酶(CarE)的活性影响,甲酸乙酯对米象表现出很高的毒力,25℃下熏蒸处理24 h的LC₅₀为28.65μL/L。亚致死剂量的甲酸乙酯可以使米象成虫体内AChE的比活力显著下降,用20μL/L的浓度处理24 h,AChE的比活力由15.684 nmol/mg.min下降至9.530 nmol/mg.min;酶动力学研究表明,甲酸乙酯可使米象成虫体内AChE的K_m值明显增加。对于羧酸酯酶,在活体条件下表现为先抑制后激活的规律,离体条件下则主要表现为抑制作用,且随着药剂浓度的增大抑制率也增大。