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

TL;DR

Microwave energy at 50°C can effectively eliminate maize weevils in corn, with optimal results at 1 minute for corn with 14% moisture.

Contribution

The study identifies optimal microwave treatment conditions for pest control while preserving grain quality.

Findings

Microwave treatment at 50°C for 1 minute effectively kills maize weevils in corn with 14% moisture.

Egg stage weevils are most susceptible to microwave energy, while adults are least affected.

Germination rates in treated corn are significantly lower than in untreated corn.

Abstract

As an eco-friendly, non-chemical method, microwave energy presents a promising alternative for the phytosanitary treatment of grain. Microwave heating is considered an efficient and rapid dielectric heating method for eliminating pests in various major grain-based stored products. Several factors affect the efficiency of microwave energy. The moisture content of the grains plays an important role in the effective application of microwave as a controlling method. Therefore, in this work, microwaves were applied at a moderate temperature of 50 °C to control the life stages of maize weevils in maize with different initial moisture contents of 10, 14, and 18%, respectively. The results showed that all maize weevil life stages were eliminated at 50 °C for 3 to 5 min; however, the most effective condition for controlling the pests and maintaining grain quality, in terms of germination rate, was found to be maize grain (14% MC) treated at 50 °C for 1 min. This condition can be further explored for industrial applications in maize processing.

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.

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