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The toxicity of sulfuryl fluoride (SF) to various pest species, the penetration of SF into flour, and the potential for any problems to arise because of fumigant cross resistance or malfunction of electronic equipment exposed to SF were studied in the UK. The pest species included Tribolium castaneum (rust-red flour beetle), T. confusum (confused flour beetle) Cryptolestes turcicus (Turkish grain beetle), Ephestia kuehniella (Mediterranean flour moth), Ptinus tectus (Australian spider beetle), Sitophilus granarius (granary weevil), Gnatocerus cornutus (broad-horned flour beetle), Tenebrio molitor (meal worm), Liposcelis bostrychophila (book louse) and Acarus siro (flour mite). For most of the pests, the egg stage was the most tolerant of fumigation, but the postembryonic stages of mites were as tolerant as the eggs. Most of the species were completely controlled by a concentration × product of 500 g h-1 m-3 at 30°C, or 1000 g h-1 m-3 at 25°C. Penetration studies into flour of 30 cm depth revealed that SF required 30 to 40 minutes to break through to this level whether or not there was forced air movement over the flour surface, and that only 2.5-3 h were required, irrespective of temperature over the range 18-28°C, for concentrations to reach 50-60% of those at the surface. At venting, 90% of the gas present in flour at 30-cm depth had dissipated after 4.5 h. Studies on phosphine-resistant and susceptible strains of T. castaneum revealed no cross resistance to SF, and repeated exposure of computer equipment to the gas revealed no malfunction. SF is a promising replacement for methyl bromide in the flour milling industry.

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Thirty-one strains of the cigarette beetle, L. serricorne, collected from tobacco in 25 countries were established on laboratory diet over a three-year period. Fourteen strains were tested with seven concentrations of phosphine (0.0034 to 0.855 g/m3) and used to develop a mortality test for phosphine resistance based on the test for other storage beetles produced by the Food and Agriculture Organization. From their probit response lines, a discriminating concentration was set at 0.17 g/m3, for 20 h, and at 25°C and 60% relative humidity. Of the 31 strains tested, 17 (55%), which originated from 12 countries and with two of unknown origin, were designated as resistant. One of the resistant strains was subjected to further treatments of phosphine to select a population homozygous for at least one major gene for phosphine resistance. Adults from this strain survived five times the discriminating concentration and the homozygous population was subsequently used in virgin crosses with the laboratory-bred, susceptible strain to produce heterozygous insects. Both the homozygotes and the heterozygotes were used to develop a more rapid knockdown resistance test, which would give results within a working day. This test requires treatment of adults with a concentration of 0.476+0.09 g/m3 phosphine for 2 h and 45 minutes.