**2. Biology, ecology, and economic importance of RPW**

The red palm weevil (RPW), *Rhynchophorus ferrugineus* (Olivier), is the most important invasive species in the genus *Rhynchophorus* that encompasses more than 10 species [22]. RPW is native to South and Southeast Asia, where it feeds on coconut, *Cocos nucifera*, as a key pest. During the past 30 years, the weevil invaded many countries around the world and is now found in 49 countries in Europe, Africa, Asia, and the American continent [23]. As far as the host range of RPW is concerned, 40 palm species are reported, including the date palm, *Phoenix dactylifera,* and the Canary Islands palm, *Phoenix canariensis* (EPPO, 2020). Thus, the

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**Figure 1.**

*Visual symptoms of red palm weevil damage on a young date palm.*

*Recent Trends in the Early Detection of the Invasive Red Palm Weevil,* Rhynchophorus…

and breakage of the trunk in advanced severe infestation (**Figure 1**).

On the other hand, infestation on Canary Island palm is exclusively at the crown

level, and the symptoms of damage include the presence of holes on the fronds, asymmetrical growth of the crown, and eventual collapse of the palm in severe infestation [26]. No recent estimate of economic losses on palms in the world due to the invasive RPW is available. However, the severe killing of palms in invaded areas has been reported [24, 25, 27]. The ecological characteristics of high fecundity, high adaptation to the environment, high mobility, and the international trade of infested planting material mediated the introduction and spread of RPW. The weevil is highly invasive and more difficult to control due to the cryptic and endophagous behavior of the immature stages and the partial cryptic behavior of the adult weevils [24]. The concealment of all developmental stages inside the palms makes early detection of the weevil at an early stage of infestation extremely difficult. Currently, the integrated management strategies adopted against RPW include early detection of infested palms, pheromone mass trapping, preventive and curative chemical treatment, removal of severely infested palms, and phytosanitary measures (**Figure 2**) [24]. Phytosanitary measures, public participation in control, and awareness campaigns reduce the probabilities of RPW infestation [28]. Any successful pest invasion passes through three important stages: introduction,

international trade of palms for plantation and landscaping purposes had resulted in the vast spread of the weevil [24, 25]. The RPW has a complete metamorphosis development; it undergoes four stages, namely, egg, larva, pupa, and adult stages. The female may lay over 200 eggs in its lifetime. The eggs hatch in 2–6 days into larvae, which last 1–3 months undergoing as many as 8 or 16 larval instars. Fully grown larvae construct a cocoon from palm fibers and undergo pupation. The pupal stage lasts for 15–30 days, after which the adult emerges. The adult weevils can live for up to 3 months, depending on abiotic and biotic factors. Adult males can be distinguished from females by the presence of a tuff of bristles on the dorsal tip of the snout, which is not found in the female [24, 26]. RPW is a multivoltine species and has a high reproductive potential where many generations can be produced per year [26]. RPW infestation on date palms occurs on the trunk near the ground level as well as on young offshoots. Palms younger than 20 years are more susceptible to attack by RPW than older palms. Infestation on male palms occurs at the crown [24]. Symptoms of damage on date palms include oozing out of brown sticky fluid with fermented odor, drying of young offshoots, ejection of chewed palm tissues,

*DOI: http://dx.doi.org/10.5772/intechopen.93393*

### *Recent Trends in the Early Detection of the Invasive Red Palm Weevil,* Rhynchophorus… *DOI: http://dx.doi.org/10.5772/intechopen.93393*

international trade of palms for plantation and landscaping purposes had resulted in the vast spread of the weevil [24, 25]. The RPW has a complete metamorphosis development; it undergoes four stages, namely, egg, larva, pupa, and adult stages. The female may lay over 200 eggs in its lifetime. The eggs hatch in 2–6 days into larvae, which last 1–3 months undergoing as many as 8 or 16 larval instars. Fully grown larvae construct a cocoon from palm fibers and undergo pupation. The pupal stage lasts for 15–30 days, after which the adult emerges. The adult weevils can live for up to 3 months, depending on abiotic and biotic factors. Adult males can be distinguished from females by the presence of a tuff of bristles on the dorsal tip of the snout, which is not found in the female [24, 26]. RPW is a multivoltine species and has a high reproductive potential where many generations can be produced per year [26]. RPW infestation on date palms occurs on the trunk near the ground level as well as on young offshoots. Palms younger than 20 years are more susceptible to attack by RPW than older palms. Infestation on male palms occurs at the crown [24]. Symptoms of damage on date palms include oozing out of brown sticky fluid with fermented odor, drying of young offshoots, ejection of chewed palm tissues, and breakage of the trunk in advanced severe infestation (**Figure 1**).

On the other hand, infestation on Canary Island palm is exclusively at the crown level, and the symptoms of damage include the presence of holes on the fronds, asymmetrical growth of the crown, and eventual collapse of the palm in severe infestation [26]. No recent estimate of economic losses on palms in the world due to the invasive RPW is available. However, the severe killing of palms in invaded areas has been reported [24, 25, 27]. The ecological characteristics of high fecundity, high adaptation to the environment, high mobility, and the international trade of infested planting material mediated the introduction and spread of RPW. The weevil is highly invasive and more difficult to control due to the cryptic and endophagous behavior of the immature stages and the partial cryptic behavior of the adult weevils [24]. The concealment of all developmental stages inside the palms makes early detection of the weevil at an early stage of infestation extremely difficult. Currently, the integrated management strategies adopted against RPW include early detection of infested palms, pheromone mass trapping, preventive and curative chemical treatment, removal of severely infested palms, and phytosanitary measures (**Figure 2**) [24]. Phytosanitary measures, public participation in control, and awareness campaigns reduce the probabilities of RPW infestation [28]. Any successful pest invasion passes through three important stages: introduction,

**Figure 1.** *Visual symptoms of red palm weevil damage on a young date palm.*

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

which is difficult because symptoms caused by the weevil are only visible when an infestation is more advanced. The highly infested palms are often destroyed and removed [2]. For this purpose, there is a requirement to use advanced technology for the early detection of the RPW. Early detection is an effective solution to control and eradicate RPW successfully. So far, the RPW detection occurs depending on the visual inspection by laborers, which is entrusted by private or public organizations. The inspection by laborers is very costly for owners of private farms; it is likely not to be implemented due to the high cost [3]. Therefore, the frequent inspection has never been applied systematically and on a large scale, even when the inspections are compulsory [4]. Although, the early detection of the RPW presence could mean a significant economization in the capital, investment in the farms, and providing job opportunities for agricultural workers [2]. RPW early detection is a major challenge due to the cryptic nature of the weevil in most of its developmental stages. RPW larva is the most dangerous stage in the pest life due to the direct destruction it causes on the infested palms. Thus, most of the early detection methods concentrate on this stage of the RPW life cycle [2, 5], although the presence of RPW adults in the palm plantation is one of the most indicative proofs of the infestation. Governments have successfully and widely used pheromone traps as the primary protocol in the integrated management to control the RPW [6, 7]. For that, the aggregation pheromone traps of RPW were included in the integrated pest management (IPM) as an essential technique to control RPW. There were unique developments in the trap designs, color, and trap density, besides the improvement of trap catching by the addition of kairomones in various forms. However, limited human resources and high transportation costs reduced the rate of monitoring and mass trapping of RPW adults [3]. Recently, there are strong ongoing efforts to develop a reliable and quick system for early detection of RPW using a combination of computer science, sensors, and modern electronic technologies. The most important and promising technologies are X-ray [2, 8, 9], acoustic systems [5, 10–17], remote sensing systems [18–21], and radio telemetry [7]. To control the RPW, it is necessary to implement an innovative and practical early detection method leading to reduce the pest population as much as possible. This action is essential, as the early detection of infested date palm trees allows the owner of farms to sanitize or to eradicate them in the event of a severe infestation. The early detection followed immediately by the palm sanitization and eradication of infested palms' parts allows to limit or prevent the RPW spread to the neighboring plantations, thus eliminating the RPW as quickly as possible [4]. The physical properties of different developmental stages of the weevil, such as sound, thermal and chemical emissions, and images are used in the early detection technologies. The main objective of this chapter is to provide an overview and engineering information about the new trends in early detection of RPW and to discuss the basic principles of the most

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current and promising technologies for RPW detection.

**2. Biology, ecology, and economic importance of RPW**

The red palm weevil (RPW), *Rhynchophorus ferrugineus* (Olivier), is the most important invasive species in the genus *Rhynchophorus* that encompasses more than 10 species [22]. RPW is native to South and Southeast Asia, where it feeds on coconut, *Cocos nucifera*, as a key pest. During the past 30 years, the weevil invaded many countries around the world and is now found in 49 countries in Europe, Africa, Asia, and the American continent [23]. As far as the host range of RPW is concerned, 40 palm species are reported, including the date palm, *Phoenix dactylifera,* and the Canary Islands palm, *Phoenix canariensis* (EPPO, 2020). Thus, the

**Figure 2.** *Conventional pheromone-food-bait trap for detection and monitoring of adult red palm weevil.*

establishment, and spread. Quarantine regulations, invasion monitoring, and eradication are the main management strategies to prevent the establishment and spread of RPW. Eradication of an invasive species depends largely on correct identification and early detection before the species is fully established in the ecosystem.
