Controlling Maize Weevil (Sitophilus zeamais) Life Stages at a Moderate Temperature Using Microwave Energy

The objective of this study is to evaluate the effect of microwave energy in controlling life stages (egg, larvae, pupa, and adults) of maize weevil (Sitophilus zeamais) and validate the optimum condition for eliminating the pest in maize grain. Maize samples (300 g) each at 10, 14, and 18% w.b. initial moisture contents (IMCs) were infested with various life stages of S. zeamais and exposed to microwave energy (2.45 GHz) at 300 W to raise the grain's temperature to 50 °C, holding for different times of 0, 1, 3, and 5 min. Among the life stages of S. zeamais, the egg stage was the most susceptible to microwave energy, whereas the adult stage was the least susceptible. Complete eradication of all life stages of S. zeamais can be achieved by using microwave energy at a temperature of 50 °C for 5 min at all initial moisture content levels. Germination rate was significantly (p < 0.05) lower in the microwave-treated grains compared to the untreated ones. The partial least squares (PLS) validation model indicated that microwave heating of grain with 14% moisture content at 50 °C for 1 min was the most effective method for eliminating S. zeamais life stages and maintaining the germination rate of the grain, which could be further explored for industrial applications in the maize processing.