FDTD simulation and experimental investigation of controlled microwave irradiation of red palm weevils

This paper presents the study made to assess the possibility of using microwave energy for irradiation of red palm weevils (Rhynchophorus ferrungineus), which is threatening palm trees in the region. The study is carried out both theoretically and experimentally. In the experimental part isolated weevils, at both larvae and adult stages, were exposed to microwave radiation, at known levels, and their mortality rate was determined. Also some parameters used as input parameters to the theoretical model are determined. Experimental results showed that 100% weevil mortality rate was obtained in exposure time between 75 seconds and 4 minutes depending on weevil type (larvae or adult), and input power level. In the theoretical side, a computer simulation model is developed using finite difference time domain (FDTD) technique and solved using a commercial package (XFDTD from Remcom, Inc). Slotted waveguide and dipole radiators were used as microwave radiators for simulation of isolated weevils and only dipole antennas for simulation of weevils embedded in tree trunk. Specific absorption rates (SAR), as well as other parameters, were computed in both cases at 2.45 GHz. Results of the isolated weevils agreed qualitatively well with experimental results in that the weevil at larvae stage absorb enough EM energy that lead to its complete destruction. Simulation of the weevil samples embedded in tree trunks showed that a significant amount of microwave energy is expended in a very small region adjacent to the dipole antenna, thus leaving a very small amount of energy for weevil irradiation. These findings are similar to those obtained experimentally by the authors in a previous study. Finally simulation results showed that FDTD technique can be effectively used for predicting microwave absorption characteristics (SAR) of the weevils and other similar pests and subsequent design and optimization of microwave radiators needed for these applications.