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United States Department of Agriculture

Agricultural Research Service

Title: Thermal Death Kinetics of Red Flour Beetle, Tribolium Castaneum (Coleoptera: Tenebrionidae)

Authors
item Johnson, Judy
item Valero, Karen
item Wang, S - WASHINGTON STATE UNIV
item Wang, J - WASHINGTON STATE UNIV

Submitted to: Journal of Economic Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: September 17, 2004
Publication Date: December 1, 2004
Citation: Johnson, J.A., Valero, K.A., Wang, S., Wang, J. 2004. Thermal death kinetics of red flour beetle, tribolium castaneum (coleoptera: tenebrionidae). Journal of Economic Entomology. 97(6):1868-1873.

Interpretive Summary: A major problem in the storage and marketing of California tree nuts is infestation by a variety of postharvest insect pests, including common stored product pests like the red flour beetle, Tribolium castaneum. Currently, the dried fruit and tree nut industry relies on fumigation with methyl bromide and phosphine for postharvest insect control. Recent concerns over resistance, regulatory action and the needs of the organic industry have generated a renewed interest in developing alternative, non-chemical treatments. Industrial radio frequency systems, extensively used in the food, textile and wood processing industries, have been suggested for control of postharvest insects. Knowledge of thermal death kinetics for targeted insects is essential in developing thermal treatments utilizing microwave or radio frequency heating. A heating block system developed at Washington State University directly heated exposed insects and is particularly useful for simulating the rapid heating rates of radio frequency treatments. In this study, we used the WSU heating block system to identify the most heat tolerant life stage of red flour beetle and determine its thermal death kinetics at a heating rate of 15°C/min. The relative heat tolerance of red flour beetle stages was found to be older larvae > pupae and adults > eggs and younger larvae. Lethal exposure times for temperatures of 48, 50, and 52°C for the most heat tolerant larval stage were next estimated. Exposures needed for 95% mortality at 48°C were too long to be practical (67 min) but increasing treatment temperatures to 50 and 52°C resulted in more useful exposure times of 8 and 1.3 min, respectively. Red flour beetle was more sensitive to changes in treatment temperature than previously studied moth species, resulting in red flour beetle being the most heat tolerant species at 48°C, but navel orangeworm, Amyelois transitella (Walker), being most heat tolerant at 50 and 52°C. Consequently, efficacious treatments for navel orangeworm at 50-52ºC would also control red flour beetle.

Technical Abstract: While developing radio frequency heat treatments for dried fruits and nuts, we used a heating block system developed by Washington State University to identify the most heat tolerant life stage of red flour beetle, Tribolium castaneum (Herbst), and determine its thermal death kinetics. Using a heating rate of 15°C/min to approximate the rapid heating of radio frequency treatments, the relative heat tolerance of red flour beetle stages was found to be older larvae > pupae and adults > eggs and younger larvae. Lethal exposure times for temperatures of 48, 50, and 52°C for the most heat tolerant larval stage were estimated using a 0.5th order kinetic model. Exposures needed for 95% mortality at 48°C were too long to be practical (67 min) but increasing treatment temperatures to 50 and 52°C resulted in more useful exposure times of 8 and 1.3 min, respectively. Red flour beetle was more sensitive to changes in treatment temperature than previously studied moth species, resulting in red flour beetle being the most heat tolerant species at 48°C, but navel orangeworm, Amyelois transitella (Walker), being most heat tolerant at 50 and 52°C. Consequently, efficacious treatments for navel orangeworm at 50-52ºC would also control red flour beetle.

Last Modified: 8/22/2014
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