Grain protectants for the control of malathion-resistant insects in stored sorghum

Duplicate experiments were carried out on bulk sorghum stored in South Queensland and in Central Queensland. Bioassays of treated grain, conducted during 6 months' storage, established that fenitrothion (12 mg kg^?1)+ bioresmethrin (1 mg kg^?1), and pirimiphos-methyl (4 mg kg^?1)+ carbaryl (8 mg kg^?1), controlled typical malathionresistant strains of Sitophilus oryzae (L.), Rhyzopertha dominica (F.), Tribolium castaneum (Herbst), and Ephestia cautella (Walker). Chlorpyrifos-methyl (10 mg kg^?1)+ pyrethrins (1.5 mg kg^?1)+ piperonyl butoxide (12 mg kg^?1), and fenitrothion (12 mg kg^?1)+ (1R)-phenothrin (1 mg kg^?1), also controlled the strains of S. oryzae, T. castaneum and E. cautella, but were only partly effective against R. dominica. Methacrifos (15 mg kg^?1) controlled all the tested species except E. cautella. Chemical assays established that the residues and rates of breakdown of these grain protectants on sorghum conformed to the general pattern for other cereal grains; residues from the above treatments were below the individual Maximum Residue Limits recommended by the Codex Alimentarius Commission.     

Fenitrothion plus (1R)-phenothrin,and pirimiphos-methyl plus carbaryl,as grain protectant combinations for wheat

Duplicate field trials were carried out on bulk wheat in commercial silos in Queensland and New South Wales. Laboratory bioassays on samples of treated grain at intervals over 9 months, using malathion-resistant strains of insects, established that treatments were generally effective. Fenitrothion (12 mg kg^?1)+ (1R)-phenothrin (2 mg kg^?1) was more effective than pirimiphos-methyl (6 mg kg^?1) + carbaryl (10 mg kg^?1) against Sitophilus oryzae (L.) and Ephestia cautella (Walker); the order of effectiveness was reversed for S. granarius (L.). Against Rhyzopertha dominica (F.), Tribolium castaneum (Herbst), T. confusum Jackquelin du Val and Oryzaephilus surinamensis (L.), both treatments effectively prevented the production of progeny. The order of persistence was pirimiphos-methyl> (1R)-phenothrin>carbaryl or fenitrothion. During processing from wheat to white bread, residues were reduced by 98% for carbaryl, >44% for (1R)-phenothrin, 98% for fenitrothion and 85% for pirimiphosmethyl.     

Insecticidal efficacy of fipronil against four stored‐product insect pests: influence of commodity,dose, exposure interval,relative humidity and temperature

BACKROUND: Fipronil is an insecticidal pyrazole that is commonly used as an insecticide in field crops, urban pesticide and veterinary medicine, but there are no reports of its evaluation against stored‐product insects. Three series of laboratory bioassays were conducted to assess fipronil as a potential grain protectant against adults of Sitophilus oryzae (L.), Tribolium confusum Jacquelin du Val, Rhyzopertha dominica (F.) and Prostephanus truncatus (Horn). Factors such as dose (0.01, 0.1, 1 and 10 mg fipronil kg^?1 grain), exposure interval (24 h, 48 h, 7 days and 14 days), temperature (20, 25 and 30 °C), relative humidity (RH; 55 and 65%) and commodity (wheat, maize, barley and paddy rice) were evaluated with regard to their impact on the insecticidal activity of fipronil. Progeny production was assessed after 64 days of exposure. RESULTS: At doses of < 1 mg fipronil kg^?1 grain, efficacy of fipronil was enhanced by an increase in temperature from 20 to 25 °C against S. oryzae or R. dominica for exposures of > 48 h and against T. confusum or P. truncatus for exposures of > 24 h. A further increase in temperature from 25 to 30 °C, although it enhanced efficacy at doses of < 1 mg fipronil kg^?1 grain against S. oryzae at all exposure intervals and against T. confusum after 7 days of exposure, it was negatively associated with efficacy against R. dominica or P. truncatus for exposures of > 24 h. By contrast, increase in RH did not have a significant impact on efficacy of fipronil. Although the performance of fipronil among the tested commodities was species dependent, this substance appeared to be less effective in paddy rice than in barley, maize and wheat. Regardless of the treated commodity, progeny production of all the tested species was almost suppressed with doses higher than 0.1 mg fipronil kg^?1 grain. CONCLUSIONS: Fipronil appeared to be a very effective alternative to the existing substances in stored‐grain protection at doses equal to or higher than 1 mg fipronil kg^?1 grain, and thus these doses require further evaluation in terms of safety for the consumer and residues on stored products. Copyright © 2010 Society of Chemical Industry     

Assessment of the grain protectants chlorpyrifos-methyl plus bioresmethrin,fenitrothion plus (1R)-phenothrin,methacrifos and pirimiphos-methyl plus carbaryl under practical conditions in Australia

Methacrifos (22.5 g t^?1) and the three protectant combinations chlorpyrifos-methyl (10 g t^?1) plus bioresmethrin (1 g t^?1), fenitrothion (12 g t^?1) plus (1R)-phenothrin (2 g t^?1) and pirimiphos-methyl (4 g t^?1) plus carbaryl (8 g t^?1) were each applied to grain that was stored in at least 15 silos. Grain temperature and levels of protectant were regularly monitored, and samples from 12 storages using each treatment were taken for laboratory assays against Rhyzopertha dominica and Tribolium castaneum. Grain condition did not deteriorate during storage. Grain remained free of insects in 60 of the 63 storages treated; partial failure in the other 3 storages was attributed to low or irregular levels of protectant. The mean and range of residue values of all protectants were recorded as a function of time and the mean observed values corresponded to predicted values. In laboratory bioassay, the order of effectiveness against T. castaneum was methacrifos > chlorpyrifos-methyl plus bioresmethrin > fenitrothion plus (1R)-phenothrin = pirimiphos-methyl plus carbaryl. The order of effectiveness against R. dominica was carbaryl plus pirimiphos-methyl = (1R)-phenothrin plus fenitrothion > methacrifos > bioresmethrin plus chlorpyrifos-methyl.     

Chlorpyrifos-methyl plus bioresmethrin; Methacrifos; Pirimiphos-methyl plus bioresmethrin; and synergised bioresmethrin as grain protectants for wheat

Field trials with various pesticide combinations were carried out on bulk wheat in commercial silos in Queensland, South Australia and Western Australia. Laboratory bioassays on samples of treated grain at intervals over 8 months using malathion-susceptible and malathion-resistant strains established the following orders of efficacy: against Sitophilus oryzae (L.), chlorpyrifos-methyl 10 mg kg^?1 + bioresmethrin 1 mg kg^?1 = methacrifos 15 mg kg^?1 in aerated storage > pirimiphos-methyl 4 or 6 mg kg^?1 + bioresmethrin 1 mg kg^?1 = bioresmethrin 4 mg kg^?1 + piperonyl butoxide 16 mg kg^?1; against Rhyzopertha dominica (F.), bioresmethrin 4 mg kg^?1 + piperonyl butoxide 16 mg kg^?1 > methacrifos 15 mg kg^?1 > chlorpyrifos-methyl 10 mg kg^?1 + bioresmethrin 1 mg kg^?1 = pirimiphos-methyl 4 or 6 mg kg^?1 + bioresmethrin 1 mg kg^?1. All treatments completely prevented production of progeny in Sitophilus granarius (L.), Tribolium castaneum (Herbst), T. confusum Jackquelin du Val and Oryzaephilus surinamensis (L.). The biological efficacy of methacrifos was greater and the rate of degradation lower in aerated than in non-aerated storage. Residue levels of all compounds were determined chemically and were below proposed international residue levels to be considered by the Codex Alimentarius Commission.     

Organophosphorothioates and synergised synthetic pyrethroids as grain protectants on bulk wheat

Organophosphorothioates and synergised synthetic pyrethroids were used in duplicate field trials carried out on bulk wheat in commercial silos in Queensland and New South Wales. Laboratory bioassays using malathion-resistant strains of insects were carried out on samples of treated grain at intervals over 9 months. These established that all treatments were generally effective. Deltamethrin (2 mg kg^?1)+ piperonyl butoxide (8 mg kg^?1), fenitrothion (12 mg kg^?1)+ fenvalerate (1 mg kg^?1)+ piperonyl butoxide (8 mg kg^?1), fenitrothion (12 mg kg^?1)+ phenothrin (2 mg kg^?1)+ piperonyl butoxide (8 mg kg^?1) and pirimiphos-methyl (4 mg kg^?1)+ permethrin (1 mg kg^?1)+ piperonyl butoxide (8 mg kg^?1) controlled common field strains of Sitophilus oryzae (L.) and Rhyzopertha dominica (F.). Against a highly resistant strain of S. oryzae, deltamethrin (2 mg kg^?1)+ piperonyl butoxide (8 mg kg^?1) was superior to the remaining treatments. All treatment combinations completely prevented progeny production in Tribolium castaneum (Herbst), T. confusum Jacquelin du Val and in Ephestia cautella (Walker). Residues of deltamethrin, fenvalerate, permethrin and phenothrin were determined and shown to be highly persistent on stored wheat. During milling, residues accumulated in the bran fractions and were reduced in white flour. They were not significantly reduced during baking.     

Efficacy of layer treatment with methoprene for control of Rhyzopertha dominica (Coleoptera: Bostrychidae) on wheat, rice and maize

BACKGROUND: Insect growth regulators are promising alternatives to traditional pesticides in stored grain. The efficacy of the juvenile hormone analogue methoprene was evaluated as a layer treatment in a laboratory experiment for control of Rhyzopertha dominica (F.) (Coleoptera: Bostrychidae) in wheat, rice and maize. RESULTS: Adults of R. dominica were placed in vials containing 33, 26 and 29 g (to a depth of 6.5 cm) of wheat, rice and maize, respectively, that was entirely or partially treated with 1, 5 or 10 mg kg^?1 methoprene. In wheat and rice, the layer treatments were not as effective as the whole‐grain treatment, but there was decreased progeny production as the application rate increased. However, on maize the partial treatments were as effective as the whole‐grain treatment at 5 and 10 mg kg^?1. CONCLUSIONS: The results suggest that partial layer treatments with methoprene can be used to control R. dominica on maize but may not be effective for control of this species on wheat and rice. Copyright © 2011 Society of Chemical Industry     

Extensive pilot use of the grain protectant combinations,fenitrothion plus bioresmethrin and pirimiphos-methyl plus bioresmethrin

Each of the combinations, bioresmethrin (1 mg kg^?1) plus pirimiphos-methyl(6 mg kg^?1) or fenitrothion (12 mg kg^?1), was applied in 1976 to grain in 21 commercial storages. Grain condition and protectant residues were regularly monitored. Three storages became infested with Rhizopertha dominica (F.), but all storages remained free of other insect species. In two of the three infested storages, application of protectant was uneven, and the third became infested only after 8 months of storage. Despite some variations in recovered residues between sites, the mean residue levels were accurately described by predictive models. Falls in temperature during storage varied considerably, and were related to factors other than climate and bin size. There was a marked effect by aeration with ambient cold air on both the grain temperature and the rate of loss of residues. Results of collaborative studies on the determination of residues indicate a need for regular check programmes of analysis, and confirm previous conclusions that residues of fenitrothion and pirimiphos-methyl can be accurately and conventionally determined.     

Efficacy of Bacillus thuringiensis Cry3Aa protoxin and protease inhibitors against coleopteran storage pests

BACKGROUND: Environmental impacts and resistance to insecticides pose serious challenges to stored‐product insect and other types of pest control. Insect‐resistant transgenic grain is a potential alternative to fumigants, but candidate control proteins are needed, especially for coleopterans. Therefore, we evaluated the efficacy of a coleopteran‐active toxin, Bacillus thuringiensis Cry3Aa, with or without protease inhibitors, in laboratory feeding assays against coleopteran storage pests. RESULTS: In a comparison of the toxicity of Cry3Aa protoxin towards three species of coleopteran storage pests, Tenebrio molitor L. was found to be most sensitive, Tribolium castaneum (Herbst.) was most refractory and Rhyzopertha dominica F. displayed an intermediate response. For R. dominica, Cry3Aa combined with 3500 mg potato carboxypeptidase inhibitor or 5000 mg aprotinin kg^?1 diet resulted in both delayed development and increased mortality. Potato carboxypeptidase inhibitor and bovine aprotinin reduced the LC₅₀ of Cry3Aa for R. dominica two‐ and threefold respectively. Cry3Aa treatment resulted in fewer progeny from R. dominica, and progeny was further reduced when the protoxin was combined with potato carboxypeptidase inhibitor. CONCLUSIONS: These data support the hypothesis that a combination of Cry3Aa protoxin and protease inhibitors, particularly a potato carboxypeptidase inhibitor, may have applications in control strategies for preventing damage to stored products and grains by coleopteran pests. Published 2011 by John Wiley & Sons, Ltd.     

The persistence and activity of insecticide spary deposits on woven polypropylene fabric

Wettable powder formulations of the organophosphorus insecticides, fenitrothion and pirimiphos-methyl, and the pyrethroids, permethrin and deltamethrin, have been compared for persistence and activity on woven polypropylene fabric; the residues produced in maize kept under the test sheets have also been measured. The test insects were Sitophilus oryzue (L.) and Tribolium custuneum (Herbst). Permethrin at 41 and 83 mg m^?2 was completely effective for the full 12 weeks of the experiment. Deltamethrin at 6.2 and 12.5 mg m^?2 was almost equally effective but after 4 weeks the deposit was slower acting against S. oryzae. The organophosphorus compounds were effective only up to 2 weeks at 250 mg m^?2 and up to 4 weeks at 500 mg m^?2. No residues could be detected under the pyrethroids but the organophosphorus insecticides gave residues of 2–4 mg kg^?1 on a thin layer of grain. This residue was biologically effective against the test insects.     

Management of five stored-product insects in wheat with pirimiphos-methyl and pirimiphos-methyl plus synergized pyrethrins

Hard red winter wheat was treated with pirimiphos-methyl at 4, 6 and 8 mg kg(-1), synergized pyrethrins at 0.38, 0.75, 1.13 and 1.5 mg kg(-1), and combinations of the two insecticides, to conduct laboratory bioassays against four beetle pests of stored grain, red flour beetle Tribolium castaneum (Herbst), rusty grain beetle Cryptolestes ferrugineus (Stephens), lesser grain borer Rhyzopertha dominica (F), and rice weevil Sitophilus oryzae (L), and one moth pest, Indianmeal moth Plodia interpunctella (Hubner). Beetle adults and P interpunctella larvae survived well on control wheat, producing a large number of progeny (65-1037 insects per container). Kernel damage in control wheat among the insect species ranged from 9 to 99%. On pirimiphos-methyl-treated wheat, mortality of R dominica adults was > or =72%, but that of the other beetle species and P interpunctella larvae was 100%. Progeny were not produced on pirimiphos-methyl-treated wheat, and the kernel damage was negligible (< or =1%). Synergized pyrethrins were ineffective against the five insect pests. Pirimiphos-methyl combined with synergized pyrethrins was not superior to pirimiphos-methyl alone against the five insect pests. Pirimiphos-methyl is not registered in the USA for use on wheat, but our results suggest that it could be a viable grain protectant at rates of 4-8 mg kg(-1).     

Organophosphorus and synergised synthetic pyrethroid insecticides as grain protectants for stored sorghum

A field experiment was carried out on bulk sorghum stored for 26 weeks in concrete silos in South Queensland. No natural infestation occurred. Laboratory bioassays of treated grain, in which malathion-resistant strains of insects were added to grain samples, indicated that all the treatments were generally effective. Deltamethrin (2mg kg⁻¹)+piperonyl butoxide (8mg kg⁻¹), fenitrothion (12mg kg⁻¹)+fenvalerate (1 mg kg⁻¹)+piperonyl butoxide (8mg kg⁻¹), and fenitrothion (12mg kg⁻¹)+phenothrin (2mg kg⁻¹)+piperonyl butoxide (8mg kg⁻¹) controlled typical malathion-resistant strains of Sitophilus oryzae (L.), Rhyzopertha dominica (F.), Tribolium castaneum (Herbst) and Ephestia cautella (Walker). Pirimiphos-methyl (6mg kg⁻¹)+permethrin (1mg kg⁻¹)+piperonyl butoxide (8mg kg⁻¹) allowed some survival of adults and progeny production by S. oryzae after 12 weeks, and by one strain of R. dominica throughout. Chemical assays established that the residues and rates of breakdown of these grain protectants on sorghum conformed to the general pattern on other cereal grains. Residues at the conclusion of the experiment were below the individual Maximum Residue Limits recommended by the Codex Alimentarius Commission.     

Toxicity of phosphine to five species of stored-product insects in atmospheres of air and nitrogen

The responses of five species of adult stored-product insects [Tribolium castaneum (Herbst), T. confusum (DuVal), Rhyzopertha dominica (F.), Sitophilus oryzae (L.) and S. granarius (L.)] to various doses of phosphine in atmospheres of air or nitrogen were determined. A few S. oryzae and S. granarius survived phosphine concentrations up to 80 mg litre^?1 for 24 h in normal (air) or nitrogen atmospheres. By contrast, T. castaneum, T. confusum and R. dominica could not tolerate more than 0.2 mg phosphine litre^?1 in air for 12 h. However, they could tolerate up to 10 mg phosphine litre^?1 in nitrogen for that period. Increasing the phosphine concentration resulted in increased mortalities of the last three species. The possible mechanism underlying this response is discussed. The reproductive potential of insects surviving phosphine exposure in a nitrogen atmosphere was unaffected.     

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     

A rapid high-pressure liquid chromatographic method for the determination of carbaryl residues in wheat grain

Carbaryl residues in wheat grain have been determined in methanol extracts using normal-phase high-pressure liquid chromatography (h. p. l. c.) with ultraviolet detection. A single-injection, clean-up and analysis technique was used to allow more rapid analysis of samples after extraction. A detection limit of 0.1 mg kg^?1 in a 50 g sample of wheat was achieved. Recoveries of 86% at the 1 mg kg^?1 level and 90-99% at the 5 mg kg^?1 level were obtained for fortified grain samples. Methanol was found to be a superior extractant for carbaryl from wheat when compared with hexane, acetone and dichloromethane. Twelve samples containing aged carbaryl residues were analysed by the h. p. l. c. technique and by a colorimetric procedure which allowed statistical analysis of errors. For the h. p. l. c. method (excluding sampling error), a relative standard deviation of 4.4% was obtained.     

Synergised cyfluthrin and cypermethrin as grain protectants on bulk wheat

Duplicate field trials were carried out on bulk wheat in commercial silos in Queensland and New South Wales. Laboratory bioassays on samples of treated grain at intervals over 8 or 9 months storage using malathion-resistant strains of insects established that treatments were generally effective. Cyfluthrin (2 mg kg^?1) plus piperonyl butoxide (10 mg kg^?1) and cypermethrin (4 mg kg^?1) plus piperonyl butoxide (10 mg kg^?1) completely controlled two strains of Sitophilus oryzae L. Control of a third strain by the cypermethrin combination was incomplete after 11/2 months and neither controlled a multi-resistant laboratory strain. Both combinations were effective against Rhyzopertha dominica F., Tribolium castaneum Herbst and Ephestia cautella Walker. No natural infestation developed in the treated grain in any silo. Mean residues of cyfluthrin and cypermethrin after 9 months storage were 58% and 52% of the calculated application rates, respectively. Compared with overall concentrations in the wheat, residue levels were higher in bran and pollard and lower in white flour. During baking, residues decreased by up to 29%. Operators experienced respiratory irritation associated with exposure to both combinations and alternative formulations would be required for use of these materials in grain storage.     

Potential of piperonyl butoxide‐synergised pyrethrins against psocids (Psocoptera: Liposcelididae) for stored‐grain protection

BACKGROUND: Piperonyl butoxide (PB)‐synergised natural pyrethrins (pyrethrin:PB ratio 1:4) were evaluated both as a grain protectant and a disinfestant against four Liposcelidid psocids: Liposcelis bostrychophila Badonnel, L. entomophila (Enderlein), L. decolor (Pearman) and L. paeta Pearman. These are key storage pests in Australia that are difficult to control with the registered grain protectants and are increasingly being reported as pests of stored products in other countries. Firstly, mortality and reproduction of adults were determined in wheat freshly treated at 0.0, 0.75, 1.5, 3 and 6 mg kg^?1 of pyrethrins + PB (1:4) at 30 ± 1 °C and 70 ± 2% RH. Next, wheat treated at 0.0, 1.5, 3 and 6 mg kg^?1 of pyrethrins + PB (1:4) was stored at 30 ± 1 °C and 70 ± 2% RH and mortality and reproduction of psocids were assessed after 0, 1.5, 3 and 4.5 months of storage. Finally, the potential of synergised pyrethrins as a disinfestant was assessed by establishing time to endpoint mortality for adult psocids exposed to wheat treated at 3 and 6 mg kg^?1 of synergised pyrethrins after 0, 3, 6, 9 and 12 h of exposure. RESULTS: Synergised pyrethrins at 6 mg kg^?1 provided 3 months of protection against all four Liposcelis spp., and at this rate complete adult mortality of these psocids can be achieved within 6 h of exposure. CONCLUSION: Piperonyl butoxide‐synergised pyrethrins have excellent potential both as a grain protectant and as a disinfestant against Liposcelidid psocids. Copyright © State of Queensland, Department of Employment, Economic Development and Innovation, 2010. Published by John Wiley and Sons, Ltd.     

Response of five species of stored-product insects to phosphine in oxygen-deficient atmospheres

Five species of stored-product insects, [Tribolium castaneum (Herbst), T. confusum (DuVal), Rhyzopertha dominica (F.), Sitophilus oryzae (L.) and S. granarius (L.)], exposed to phosphine in nitrogen and various oxygen-deficient atmospheres, showed reduced susceptibility to three concentrations of phosphine (0.02, 0.04 and 0.2 mg litre^?1). The last two species also showed reduced susceptibility to phosphine at 2.0 mg litre^?1. Generally mortality increased progressively as the level of oxygen was raised. There was a close relationship between the ability of insects to withstand anoxia and survival from phosphine treatment.     

Efficacy of Surface Dust Treatments of Pirimiphos-Methyl and Etrimfos when Applied to Commercially Stored Wheat and Barley

Commercially stored wheat and barley were surface treated with dust formulations of pirimiphos-methyl and etrimfos at the manufacturer's recommended application rate. Samples were taken at four-weekly intervals for 32 and 16 weeks for wheat and barley respectively. Pesticide efficacy was determined using insect bioassays and chemical analysis of residues. There was no evidence to suggest a decline in residue levels of either pesticide over the experimental period. However, considerable variation was observed in the residue levels recorded at different sample points and also between residue levels recorded for the same point over the trial period. Control of susceptible strains of Tribolium castaneum (Herbst), Oryzaephilus surinamensis (L.) and Sitophilus granarius (L.) was achieved where recovered pesticide residues remained above 1 mg kg⁻¹ pirimiphos-methyl and 1·6 mg kg⁻¹ etrimfos.     

Ethyl formate plus methyl isothiocyanate--a potential liquid fumigant for stored grains

BACKGROUND: Methyl bromide is being phased out for use on stored commodities, as it is listed as an ozone‐depleting substance, and phosphine is the fumigant widely used on grains. However, phosphine resistance occurs worldwide, and phosphine fumigation requires a long exposure period and temperatures of > 15 °C. There is an urgent requirement for the development of a fumigant that kills insects quickly and for phosphine resistance management. This paper reports on a new fumigant formulation of 95% ethyl formate plus 5% methyl isothiocyanate as an alternative fumigant for stored grains. RESULTS: The formulation is stable for at least 4 months of storage at 45 °C. A laboratory bioassay with the formulation showed that it controlled all stages of Sitophilus oryzae (L.), Sitophilus granarius (L.), Tribolium castaneum (Herbst), Rhyzopertha dominica (F.), Trogoderma variabile Ballion and Callosobruchus maculatus (Fabricius) in infested wheat, barley, oats and peas at 80 mg L^?1 for 5 days, and in canola at both 40 mg L^?1 for 5 days and 80 mg L^?1 for 2 days at 25 ± 2 °C. After an 8–14 day holding period, residues of ethyl formate and methyl isothiocyanate in wheat, barley, peas and canola were below the experimental permit levels of 1.0 and 0.1 mg kg^?1. However, fumigated oats needed an 18 day holding period. CONCLUSIONS: The findings suggest that the ethyl formate plus methyl isothiocyanate formulation has potential as a fumigant for the control of stored‐grain insect pests in various commodities. Copyright © 2011 Society of Chemical Industry