Efficacy of heat treatment on phosphine resistant and susceptible populations of stored product insects

In this study we evaluated the efficacy of heat treatment on phosphine resistant and susceptible populations of stored product insects at twenty three different commercial facilities in Greece. Heat treatments were carried out by using special equipment, such as Therminate, TempAir and ThermoNox, applied alone or in combination. The overall temperature range was between 33 and 55 degrees C and the duration of the heat treatments was between 20 and 39 h. Adults of the lesser grain borer, Rhyzopertha dominica (F.) (Coleoptera: Bostrychidae), and the sawtoothed grain beetle, Oryzaephilus surinamensis (L.) (Coleoptera: Silvanidae), were used in the experiments. The field populations were collected from different storage facilities in Greece and were characterized as resistant populations by using the Detia Degesch Phosphine Tolerance Test Kit. Insect mortality was measured at the termination of each trial. Then, the vials were kept in incubator chambers at 25 degrees C and 65% relative humidity and 65 d later the progeny production was measured in the treated substrate. In light of our findings, in the vast majority of the cases, complete control was observed for both resistant and susceptible populations at all facilities. In general, in the few cases where survival and progeny production was recorded, there was no specific trend towards specific species or population. Overall, based on the current results, heat treatment can be used by the industry as an alternative method for the control of phosphine-resistant adults of R. dominica and O. surinamensis. (C) 2018 Published by Elsevier Ltd.