**4. Conclusion**

*Invasive Species - Introduction Pathways, Economic Impact, and Possible Management Options*

to cost-intensive record data for GIS modeling approaches [42].

*The electromagnetic spectrum as a function of wavelength (m) and frequency (Hz).*

**Overview:** X-rays are forms of electromagnetic radiation (similar to visible lights), as shown in **Figure 6**, but unlike the visible light, X-rays have higher energy and can pass through most materials and objects including the material to be tested due to its high frequency (1018 Hz) and low wavelength (10−10 m). X-rays are used in a quick nondestructive test that produces images of the different objects and structures inside the material. The beams of X-ray pass through the material, and they are absorbed in different amounts in the materials they pass through depending on the density of each material. Whenever the material is dense, it appears as white color, while the fatty objects appear as gray shades, and the empty spaces show up as black. X-rays are used to create images of objects, hole space, and tissues in the trunk of palm trees. When X-rays pass through the material, it will also pass through a detector of the X-ray on the other side, creating an image based on the shadows, which are formed by the objects, tissues, and empty spaces inside the material. In agricultural applications, types of detectors of X-rays that produce digital images are used. The digital X-ray image produced from this case is defined as "radiograph" [43].

**Application of X-rays:** To detect the RPW using a radiograph, two X-rays parts (X-ray source and X-ray detector) are placed around the trunk of the palm tree (in

Tree Radar Unit TRU™, a densitometer, and a penetrometer) to detect RPW in Italy and KSA. In Italy, the thermal camera showed a high accuracy of 96.29% and the digital camera showed an accuracy of 92.6% compared to close visual inspection. Tree Radar Unit and densitometer additionally showed great accuracy of 83.33 and 88.9%, respectively. In the Kingdom of Saudi Arabia, the thermal camera showed an accuracy of 77.7% compared to invasive determination. While the digital camera revealed a lower accuracy of 66.7%. TRU™ also provided an accuracy of 74.7% compared to invasive diagnosis. The satisfying conclusions taken using the application of remote sensing are good as a starting point to develop an integrated protocol for the early detection of RPW and control strategies [40]. A study was conducted to analyze the fitness of "8-band WorldView-2 satellite imagery" for detecting the tree infested by bark beetle at two intensity stages of dead and green attack versus the healthy trees. The results showed that "WorldView-2 satellite" information might be helpful for large-scale applications aiming at early detection of bark beetle infestation with the remote sensing data. Despite this, the information seemed uncertain to identify each tree at the green attack of the infestation stage, but this information can be used for the remotely sensed maps of bark beetle infestation, which can be used also positively as a contributor to the bark beetle modeling community. The remotely sensed maps can be used also as an alternative application

**42**

**Figure 6.**

**3.3 X-ray**

Red palm weevil (RPW) causes massive economic losses in the date palm production sector as well as ornamental palms used in landscape worldwide. The most important challenges of RPW detection in the early stages are the presence of a few externally visible signs upon which detection can be based. Early detection is essential to initiate a rapid response to the eradication and effective treatment of RPW. The most effective techniques currently used for early detection of the RPW rely mainly on visual inspection and pheromone trapping. Dependence on the traditional method of visual inspection of palm trees to detect the RPW and other pest infestations is both time consuming and laborious. Additionally, visual inspection is only effective in a more advanced stage of infestation. Recently, the emphasis has been on using the modern technologies and development of systems and devices for early detection of the infestations in palm trees, especially the infestation by RPW. The most important applications of experimented technology were X-rays, remote sensing systems, acoustic sensors and software, bioacoustic applications, thermal image, X-rays, CT, etc. Modern alternative techniques have been undertaken for the early detection of the RPW infestations to reduce the dependence on visual inspection, which is expensive and requires highly trained labor. Most modern detection methods have their strength and weaknesses. However, an effective, applicable, and direct method for early detection of RPW, at all life stages inside the palm trees,

remains to be developed. Therefore, to increase the overall reliability and efficiency of early detection, there is a need for further research and experiments to develop and produce reliable, easy-to-handle, and cost-effective portable detection systems for RPW early detection. Based on the findings of previous studies, we particularly mention promising technologies such as acoustic and remote sensing systems, thermal imaging, and the X-rays.
