Impact of short-term heat pre-treatment at 50 °C on the toxicity of contact insecticides to adults of three Sitophilus granarius (L.) populations

For field and selected weevils, heat pre-treatment at 50 °C over the PT80 increased deltamethrin and dichlorvos toxicity to selected populations, but not to field populations when compared to their toxicity without pre-heating. Deltamethrin and dichlorvos toxicity after a 72-h recovery period from heat treatment over the PT80 was higher to the selected population than to the resistant field population. Compared to the Lab strain, deltamethrin demonstrated lower toxicity to selected weevils and especially to a field population, while dichlorvos was considerably more toxic to both populations.