RESISTANCE TO GRAIN-PROTECTANT INSECTICIDES IN COLEOPTEROUS PESTS OF STORED CEREALS IN QUEENSLAND, AUSTRALIA

Samples of field populations of Cryptolestes spp., Oryzaephilus surinamensis (L.), Rhyzopertha dominica (F.), Sitophilus oryzae (L.), and Tribolium castaneum (Herbst) were collected from central storages, grain merchants, and farms in Queensland, Australia. First-generation progeny of each sample were exposed to grain treated with commercial formulations of insecticides. These concentrations were chosen to detect new resistances to fenitrothion in T. castaneum, S. oryzae, and Cryptolestes spp., resistance to bioresmethrin + piperonyl butoxide (PB) in R. dominica, and increases in the frequency of resistance to fenitrothion and chlorpyrifos-methyl in O. surinamensis. No new resistance to fenitrothion was detected in T. castaneum, S. oryzae, or Cryptolestes spp. High-level resistance to bioresmethrin + PB (resistance factor almost-equal-to 130) was detected at three central storages but not on farms or with grain merchants. High-level resistance to fenitrothion was present in almost all O. surinamensis samples from central storages and in more than half the farm samples collected. Resistance to chlorpyrifos-methyl that could result in control failures was detected in 60% of farm samples and in about 40% of samples collected from central storages.