Abstract
The objectives of this work were to assess phosphine resistance in insect populations (Tribolium castaneum, Rhyzopertha dominica, Sitophilus zeamais and Oryzaephilus surinamensis) from different regions of Brazil and to verify if the prevailing mechanism of phosphine resistance in these populations involves reduced respiration rates. Sixteen populations of T. castaneum, 15 of R. dominica, 27 of S. zeamais and eight of O. surinamensis were collected from 36 locations over seven Brazilian states. Each population was tested for resistance to phosphine, based on the response of adults to discriminating concentrations, according to FAO standard method. For each insect species, the production of carbon dioxide of the most resistant and of the most susceptible populations was inversely related to their phosphine resistance. The screening tests identified possible phosphine resistant populations. R. dominica and O. surinamensis were less susceptible to phosphine than the other two species. The populations with lower respiration rate showed a lower mortality at discriminating concentration, possibly related to a phosphine resistance mechanism. Phosphine resistance occurs in stored-product insects, in different regions of Brazil, and the resistance mechanism involves reduced respiration rate.
Highlights
Phosphine is the primary fumigant used to protect the majority of the world’s grain and a variety of other stored commodities against insect pests (Daglish, 2004; Collins et al, 2005)
Sixteen populations of T. castaneum, 15 of R. dominica, 27 of S. zeamais and eight of O. surinamensis were collected from 36 locations over seven states of Brazil (Table 1)
Broken corn kernels were used as food for T. castaneum and O. surinamensis, whole corn kernels for S. zeamais, and whole wheat kernels for R. dominica (13% moisture content)
Summary
Phosphine is the primary fumigant used to protect the majority of the world’s grain and a variety of other stored commodities against insect pests (Daglish, 2004; Collins et al, 2005). Phosphine plays an important role for protection especially because of its low cost, fast dispersion in the air, low residues, and human intolerance to contact pesticides These advantages have contributed to increased dependence on this fumigant (Chaudhry, 2000; Hasan & Reichmuth, 2004; Wang et al, 2006). The lack of ideal airtight conditions for fumigation, in most storage units, increases the frequency of control failures and, increases the frequency of applications (Pacheco et al, 1990; Chaudhry, 2000; Benhalima et al, 2004; Lorini et al, 2007) These factors combine to result in higher selection pressure for phosphine resistance (Bengston et al, 1999; Collins et al, 2002)
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