Resistance to fumigants has been frequently reported in insect pests of stored products and is one of the obstacles in controlling these pests. The authors studied phosphine resistance and its physiological basis in adult insects of 12 populations of Tribolium castaneum (Herbst) (Tenebrionidae), ten populations of Rhyzopertha dominica (F.) (Bostrichidae) and eight populations of Oryzaephilus surinamensis L. (Silvanidae) from Brazil, and the possible existence of fitness costs associated with phosphine resistance in the absence of this fumigant. The bioassays for the detection of phosphine resistance followed the FAO standard method. The production of carbon dioxide and the instantaneous rate of population increase (r(i)) of each population of each species were correlated with their resistance ratios at the LC(50). The resistance ratio at LC(50) in T. castaneum ranged from 1.0- to 186.2-fold, in R. dominica from 2.0- to 71.0-fold and in O. surinamensis from 1.9- to 32.2-fold. Ten populations of T. castaneum, nine populations of R. dominica and seven populations of O. surinamensis were resistant to phosphine. In all three species there was significant association (P < 0.05) between respiration rate and phosphine resistance. The populations with lower carbon dioxide production showed a higher resistance ratio, suggesting that the lower respiration rate is the physiological basis of phosphine resistance by reducing the fumigant uptake in the resistant insects. Conversely, populations with higher r(i) showed lower resistance ratios, which could indicate a lower rate of reproduction of the resistant populations compared with susceptible populations. Thus, management strategies based on the interruption of phosphine fumigation may result in reestablishment of susceptibility, and shows good potential for more effective management of phosphine-resistant populations.

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It was concluded that ozone is an important alternative for peanut detoxification because it is effective in controlling potentially aflatoxigenic fungi and also acts in the reduction of aflatoxin levels in kernels.

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-The resistance to fumigant insecticides in stored-products insects is often recorded. Several factors influence the evolution of insecticide resistance. Among these, the frequency of applications and the migration of resistant populations are of primary importance for the stored-product insects. The aim of this study was to characterize the spectrum and investigate the status of phosphine resistance in Brazil, in 13 populations of the coleoptera Tribolium castaneum Herbst (Tenebrionidae), ten populations of Rhyzopertha dominica (Fabr.) (Bostrichidae), and eight populations of Oryzaephilus surinamensis (L.) (Silvanidae). The pattern of resistance dispersion in the populations of these species was also verified. The bioassays for the detection of phosphine resistance followed the FAO standard method. To test the influence of migration in the evolution of the phosphine resistance, the difference of mortality in the discriminating concentration and the geographical distance among each pair wise combination of collection sites were correlated. None of the populations exhibited mortality above 90% in the discriminating concentration, for the three species. Mortality in the discriminating concentration increased with the geographical distance for R. dominica and O. surinamensis. However, no significant linear response was observed among the variables for T. castaneum populations. These results suggest that the dispersion of insects and the local selection are relevant in the evolution of the phosphine resistance in populations of R. dominica and O. surinamensis. In contrast, grain trade and local selection are probably the factors that determine the evolution of the phosphine resistance in populations of T. castaneum.