Insecticidal effect of nitrogen on stored-product beetle populations with different susceptibility levels to phosphine in commercial chambers and silos

Abstract: We evaluated nitrogen treatment on phosphine susceptible and resistant populations of three different beetle species: Tribolium castaneum (Herbst) (Coleoptera: Tenebrionidae), Sitophilus oryzae (L.) (Coleoptera: Curculionidae) and Oryzaephilus surinamensis (L.) (Coleoptera: Silvanidae). The trials were conducted in two different structures (chambers and silos), with the oxygen level to be lower than 1 %. In chambers, different temperatures and exposure times were evaluated. In silos, the trials were conducted for 30 and 20 days. For each trial, vials with insects were placed in different locations inside each structure. Our results, suggest that high mortality was recorded in most of the cases tested. Almost 100 % mortality was recorded in chamber and some survival was recorded in silos, regardless of the phosphine resistance level of the populations that had been tested. Overall, our results indicated that nitrogen is effective against stored product insects, while structure, exposure time and temperature are key parameters for complete control.