Research Institute for Sustainable Humanosphere, Kyoto University, Uji, 611-0011, Japan.
Nara University of Education, Takabatake-cho, Nara, 630-8528, Japan.
Sci Rep. 2020 Mar 23;10(1):5197. doi: 10.1038/s41598-020-61902-6.
Demands for chemical-free treatments for controlling insect pests are increasing worldwide. One such treatment is microwave heating; however, two critical issues arise when using microwaves as a heat source: intensive labor and excessive energy-consumption. Optimization is thus required to reduce energy consumption while effectively killing insects. Currently, the lethal effect of microwaves on insects is considered to be due to the temperature of the irradiated materials. This study examines how the conditions of irradiation, such as resonance or traveling mode, changed the conversion of electromagnetic energy into heat when 2.45 GHz microwaves penetrated the body of the termite, C. formosanus. Our results indicated that it is possible to heat and kill termites with microwaves under resonance condition. Termites were however found to be very tolerant to microwave irradiation as the permittivity of the insect was low compared with other reported insects and plants. Electron spin resonance revealed that termites contained several paramagnetic substances in their bodies, such as Fe, Cu, Mn, and organic radicals. Interestingly, irradiation with traveling microwaves hardly produced heat, but increased the organic radicals in termite bodies indicating non-thermal effects of microwaves.
全世界对控制虫害的无化学处理方法的需求正在增加。微波加热就是一种这样的处理方法；然而，当微波被用作热源时，会出现两个关键问题：劳动强度大且能源消耗过多。因此，需要进行优化以减少能源消耗，同时有效地杀死昆虫。目前，认为微波对昆虫的致死作用是由于被照射材料的温度。本研究探讨了在 2.45GHz 微波穿透白蚁，C. formosanus 的身体时，照射条件（如共振或行波模式）如何改变电磁能向热能的转换。我们的结果表明，在共振条件下，有可能利用微波加热和杀死白蚁。然而，由于与其他报道的昆虫和植物相比，昆虫的介电常数较低，白蚁对微波辐射具有很强的耐受性。电子顺磁共振显示，白蚁体内含有几种顺磁物质，如 Fe、Cu、Mn 和有机自由基。有趣的是，行波照射几乎没有产生热量，但增加了白蚁体内的有机自由基，表明微波具有非热效应。
