High-power microwave radiation as an alternative insect control method for stored products

Insect mortality studies were performed with a high-power microwave source operating at a frequency of 10.6 GHz at power levels of 9-20 kW to irradiate samples of soft white wheat, Triticum aestivum (L.), infested with maize weevil, Sitophilus zeamais Motschulsky, and ground wheat infested with red flour beetle, Tribolium castaneum (Herbst). These pests are common internal and external feeders in stored products, respectively. Samples at various age intervals from egg to adult were exposed. The results support the hypothesis that the insect-to-host dissipation ratio increases at frequencies >2.45 GHz. Mean mortalities ≤93% occurred for all ages of S. zeamais and ≤94% for adults and larvae of T. castaneum for mean specific input energies of ≤51 J/g and 53 J/g, respectively, indicating that S. zeamais is more susceptible. Extrapolating the results to the cost of treating the product in bulk volume at a busbar electric energy cost of $0.05 per kW-h (3,600 kJ) indicates a unit cost for electric energy ranging only from $0.056 per bushel of wheat infested with S. zeamais to $0.139 per hundred weight of ground wheat infested with T. castaneum.