A modelling study of the effects of temperature manipulation upon the control of Sitophilus oryzae (Coleoptera: Curculionidae) by insecticide.
A model for the population growth of Sitophilus oryzae was modified to include new data on variable developmental period, to improve computational efficacy and to consider the effect of insecticides upon adult survival, where insecticide toxicity and rate of breakdown are dependent upon temperature. The model was used to consider the effect of grain cooling on population growth under typical Australian conditions: by itself, after fumigation or combined with treatment with a residual insecticide. Cooling the grain to 15°C, no matter how rapidly, was insufficient to prevent population growth. Cooling after fumigation gave some long-term protection when the rate of cooling was rapid. The effects of grain cooling used together with insecticide treatment depended on the type of insecticide employed. With pyrethroids, the effect was beneficial and the application rates necessary for control could be reduced to <20% of normal. With very stable organophosphorus insecticides the benefits were less obvious, because of the positive temperature-toxicity relationship.