Effects of flameless catalytic infrared radiation on Sitophilus oryzae (L.) life stages q Moses Khamis a , Bhadriraju Subramanyam a, * , Hulya Dogan a , Paul W. Flinn b , Jeffrey A. Gwirtz a a Department of Grain Science and Industry, 201 Shellenberger Hall, Kansas State University, Manhattan, KS 66506, USA b USDA-ARS, Center for Grain and Animal Health Research, Manhattan, KS 66502, USA article info Article history: Accepted 8 November 2010 Keywords: Infrared energy Rice weevil Stored wheat Grain disinfestation Efficacy assessment abstract A laboratory benchtop flameless catalytic infrared emitter was evaluated against all life stages of the rice weevil, Sitophilus oryzae (L.), an insect species associated with stored wheat. The emitted infrared radiation was in the 3e7 mm range. A non-contact infrared thermometer measured grain temperatures continuously during exposures of infested wheat. Insect mortality was a function of the final grain temperature attained. In general, higher grain temperatures were attained when using 113.5 versus 227.0 g of wheat, and at 8.0 cm from the emitter versus 12.7 cm, and during a 60 s exposure versus a 45 s exposure. Complete mortality of all life stages of S. oryzae was achieved at 8.0 cm from the emitter using 113.5 g of wheat, with a 60 s exposure; the mean grain temperatures attained ranged from 108.4 to 111.8  C. The log odds ratio tests showed that eggs (0 days old) were the least susceptible stage to infrared radiation, followed by adults within kernels (28 days old), pupae (24 days old), young larvae (7 days old), larvae that were 14e21 days old, and adults (42 days old). These data using small amounts of grain indicate infrared radiation from the flameless catalytic emitter to be a viable option for disinfesting wheat containing various life stages of S. oryzae. Ó 2011 Elsevier Ltd. All rights reserved. 1. Introduction Gas fired infrared radiation was evaluated three to four decades ago for its capacity to disinfest rice and other cereal grains (Tilton and Schroeder, 1961, 1963; Cogburn, 1967; Cogburn et al., 1971; Kirkpatrick and Tilton, 1972; Kirkpatrick et al., 1972; Tilton et al., 1972, 1983). The gas fired infrared radiation was generated with propane combusted on ceramic tiles producing more than 14.07 kW/h (48,000 BTU/h) of heat energy (Tilton and Schroeder, 1961; Kirkpatrick and Cagle, 1978). However, these gas fired infrared emitters had an open flame and produced temperatures in excess of 900  C. Such high temperatures and open flames are not suitable for use in dusty grain storage and handling facilities due to explosion hazards. In previous evaluations of infrared radiation, different life stages of insects developing within kernels were not mentioned, and the grain temperatures were measured after infrared exposure and not in “real time”, which resulted in under- reporting actual temperatures attained by the grain. Flameless catalytic infrared radiation is a new technology devel- oped by Catalytic Drying Technologies LLC, Independence, KS, USA (www.catalyticdrying.com). It has been used primarily in the natural gas industry to heat pipes and in the automobile industry to dry paints, in addition to drying and disinfesting cereal grains (Pan et al., 2008). The flameless infrared radiation is emitted when propane or natural gas is combusted in the presence of a platinum catalyst resulting in temperatures of about 400  C at the emitter surface. The only other co-products of this chemical reaction are water vapor and carbon dioxide (Gabel et al., 2006; Pan et al., 2008). Infrared radiation has been successfully used to inactivate enzymes and pathogenic bacteria, dehydrate food commodities, and disinfest durable commodities (Sandu, 1986; Gabel et al., 2006; Pan et al., 2008). In the present investigation, the effectiveness of flameless catalytic infrared radiation was evaluated against different life stages of the rice weevil, Sitophilus oryzae (L.) (Coleoptera: Curcu- lionidae), an economically important internal pest of stored wheat (Sinha and Watters, 1985). Specific objectives were to examine the influence of grain quantity, distance from the infrared emitter, and exposure time on the susceptibility of S. oryzae eggs, larvae, pupae, and adults. 2. Materials and methods 2.1. Insect rearing Cultures of S. oryzae were reared on 12% moisture content, organic, hard red winter wheat (var. Jagger), obtained from Heart- land Mills, Marienthal, KS, USA, at 28  C, 65% relative humidity (r.h.), q Mention of trade or proprietary names in this publication does not imply an endorsement by Kansas State University or the USDA. * Corresponding author. Tel.: þ1 785 532 4092; fax: þ1 785 532 7010. E-mail address: sbhadrir@k-state.edu (B. Subramanyam). Contents lists available at ScienceDirect Journal of Stored Products Research journal homepage: www.elsevier.com/locate/jspr 0022-474X/$ e see front matter Ó 2011 Elsevier Ltd. All rights reserved. doi:10.1016/j.jspr.2010.11.002 Journal of Stored Products Research 47 (2011) 173e178