Phosphine resistance in the Philippines
2018
Acda, M.A. | Mangoba, M.A. | Mesa, V.G. | Dela Cruz, M.V.
Resistance to phosphine is a threat to its continued use as a grain fumigant. Reports of increasing frequency of fumigation failures in the industry make it necessary to look into the possible development of phosphine resistance in major stored product pests. Seventeen strains of Rhyzopertha dominica (Fabricius). 40 of Sitophilus spp., 28 of Tribolium castaneum (Herbst), 38 of Oryzaephilus surinamensis (L.), and nine of Cryptolestes ferrugenius Stephens were collected from 29 provinces nationwide and tested for phosphine resistance following the recommended method by the Food and Agriculture Organization. Results were validated in full assay tests and insect responses were analysed by probit-generating concentration-mortality curves. Resistance factors were established using the LC sub 99 of susceptible and resistant strains. Results showed that phosphine resistance is already widespread in the Philippines, with very high level of resistance detected in a strain of R.dominica (x1138). Phosphine resistance was also detected in O. surinamensis and C. ferrugenius. Meanwhile, low levels of resistance were observed in T. castaneum while Sitophilus spp. remains susceptible.
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