Baseline Responses to Phosphine and Resistance Status of Stored-Grain Beetle Pests in Queensland, Australia

Abstract

Laboratory strains and field populations of Rhyzopertha dominica (F.), Sitophilus Oryzae (L.), Oryzaephilus surinamensis (L.), and Tribolium castaneum (Herbst) from Queensland, Australia, were tested with a range of concentrations of phosphine. Based on these tests, concentrations that could be used with a 20-h exposure to discriminate between susceptible and resistant individuals for the four species were (mg/liter) 0.03, 0.04, 0.04, and 0.03. Other concentrations were needed to discriminate between detected resistance and possible higher level resistance. Discriminating concentration tests showed that resistance to phosphine was common in field populations of R. dominica and S. oryzae, but not in O. surinamensis or T. castaneum. Resistance factors based on 20-h exposures of selected resistant strains were 20 times for R. dominica, four times for S. oryzae, and three times for O. surinamensis.