Heat treatment of grain-processing facilities for insect management: a historical overview and recent advances

Purpose of review: Tactics to manage infestations of stored-product insects in grain-processing facilities historically included the use of heat treatments and the fumigant methyl bromide. The phase out of methyl bromide in the USA in 2005, because of its adverse effects on stratospheric ozone, has renewed interest in using heat treatments. In this review, a brief history regarding the use of heat treatments in grain-processing facilities, such as flour mills, is described along with recent research developments and future research needs. Findings: Scientific literature published during the last decade shed new light on the following areas: identification of a heat-tolerant stage of a species based on stage-specific susceptibility at different constant elevated temperatures; differences in susceptibi lity among stored-product insect species to elevated temperatures; confusion in determining a heat -tolerant stage during commercial heat treatments of grain-processing facilities; impact of sanitation on insect responses; degree and duration of insect suppression obtain ed following a heat treatment intervention; development and validation of a thermal death kinetic model to predict survival of heat -tolerant insect life stages as a function of time-dependent temperature data; and development of software programs to estimate the heat e nergy required including costs of a heat treatment based on fuel used and predicting survival of heat-tolerant insect stages in “real time” during heat treatments. Directions for future research: Temperature-time mortality relationships have been developed for a few economically important insect species and additional species should be evaluated in both laboratory and field conditions. Very little is understood about the impact of the lethal and sub-lethal elevated temperatures used during heat treatments on insect behaviour and reproduction. The costeffectiveness of combining elevated temperatures with other chemical or nonchemical methods in grain-processing facilities also should be explored.