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Subramanyam Lab

Heat & IPM

Project Title: Use of high temperatures for managing insects in flour and feed mills.

Investigators: Rizana Mahroof, Anna Getchell, and Bh. Subramanyam

Objectives: To determine the temperatures attained during heat treatment of mills outside and inside equipment; influence of heat on all life stages of caged insects; determine impact of relative humidity on insect mortality; develop predictive models to estimate heat required to kill insects in the laboratory and evaluate models in the field.

Methods: Field studies will be conducted during actual heat treatment of Kansas State University pilot flour and feed mills or actual mills in the US, and laboratory studies will be conducted using a programmable oven. HOBO units will be used to monitor temperature and relative humidity during a heat treatment outside and inside pieces of equipment. A range of humidities and their impact in killing insects during a heat treatment will be studied by placing insects inside plastic cereal holders. Glycerol solutions of different specific gravities will be used to alter humidity. Insect species that will be exposed include: the red flour beetle, cigarette beetle, and Indianmeal moth. Life stages of insects will be exposed to various time periods during an actual (field) or simulated (laboratory) heat treatment to determine acute and delayed mortality, and reproductive potential of insects exposed to high temperatures. Experiments will be run at constant temperatures above 40°C to establish a lower temperature threshold for accumulating temperatures and to develop a degree-hour model to predict insect mortality. Field validation of the model will be conducted during an actual heat treatment and HOBO and insect bioassay data will be used for model validation.

A JPG image shows a photo of rupp heaters used in Heat Treatment of Feed Mills.

Rupp Heaters used in Heat Treatment of Feed Mills

Impacts: Presently, very few scientific papers have characterized temperature distributions within a mill being heat treated, and only a few papers have studied the acute and delayed effects of heat on insects. Our research will provide a more quantitative and practical basis for evaluating effectiveness of heat treatments in killing insects, and may suggest a minimum temperature and time than the currently recommended exposure of 24 hours at or above 50°C.