**3. Host range and introduction pathways**

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

strategies. These include early detection of the weevil infestation, limitation of its biological control agents under field conditions and lack of farmers' participation in the control operations [2]. The aim of this chapter is to give a consolidated information on gaps and challenges in current RPW management as well as future prospects.

During the mid-1980s, RPW was reported on date palm *Phoenix dactylifera* L. from the United Arab Emirates in the Gulf region of the Middle East. Subsequently, first reports of RPW invasion came from the other Gulf countries of the Middle East. During 1993, RPW attack was reported on date palm in Egypt in North Africa, and later during 1995, it was detected for the first time on *P. canariensis* from Spain in Europe. During the next two decades, the pest spread rapidly in the Gulf region of the Middle East, some Maghreb countries in North Africa and the Mediterranean basin countries in Europe (**Figure 1**). RPW has rapidly expanded its geographical range during the last three decades, and ecological niche modeling [3] suggests that the pest is likely to expand its geographical range still further. Recent reports of RPW invasion suggest that the pest is establishing in East Africa in Djibouti on date palm and also in the Caucasian region where it is detected in Abkhazia on the canary island palm in the Republic of Georgia. During 2019, RPW was detected in Bulgaria in the Black Sea Basin region and also in Bosnia-Herzegovina in Southeastern Europe.

The only report of RPW invasion in the American continent comes from Aruba and Curacao islands in the Caribbean region [4]. Although RPW was reported from California, USA, during 2010 [5], molecular studies at the University of California, USA, subsequently characterized the pest as *R. vulneratus* [6], a closely related species of *R. ferrugineus* predominant on coconut in the South East Asia. Similarly, the previous *R. ferrugineus* reports from Australia and countries in the Oceanic region have now been attributed to other species of the *Rhynchophorus* group of weevils. It is pertinent to point out that although RPW moves through infested offshoots in the date palm-growing countries, another important route of transmission/movement

of the pest is through palms shipped for ornamental gardening.

*Current Geographical Distribution of RPW (Source- EPPO 2020; https://gd.eppo.int/taxon/RHYCFE/*

**2. Global RPW invasion: an update**

**4**

**Figure 1.**

*datasheet).*

As the geographical range of the pest expanded, so did the host range of RPW. During the mid-1950s, RPW was reported from just four palm species, viz. *C. nucifera*, *P. dactylifera, Metroxylon sagu* and *Corypha umbraculifera* [8]. RPW is currently reported on 40 palm species worldwide [7, 9, 10], including *Areca catechu* L., *Arenga saccharifera* Labill, *A. engleri* Becc., *A. pinnata* (Wurmb), *Bismarckia nobilis* Hildebrand and Wend, *Borassus flabellifer* L., *B*. sp., *Brahea armata S. Watson*, *B*. *edulis*, *Butia capitata* (Mart.) Becc., *Calamus merrillii* Becc., *Caryota cumingii* Lodd., *C. maxima* Blume, *Cocos nucifera*, *Corypha utan* Lamk., (= *C*. *gebanga*, *C. elata*), *C*. *umbraculifera* L., *Chamæerops humilis*, *Elaeis guineensis*, *Livistona australis* (R.Br.) Mart., *L. decipiens* Becc., *L. chinensis* Jacq.R. Br., *L*. *saribus* (= *L*. *cochinchinensis*) (Lour.) Merr., *Metroxylon sagu* Rottb., *Oncosperma horrida* (Scheff.), *O*. *tigillarium* (Ridl.), *Phoenix canariensis* (Chabaud), *P. dactylifera*, *P*. *roebelinii* O'Brien, *P. sylvestris* Roxb, *P*. *theophrastii* Greuter, *Pritchardia pacifica* Seemann and Wendland, *P. hillebrandii* (Kuntze) Becc., *Ravenea rivularis* Jumelle and Perrier, *Roystonea regia* (Kunth.), *Sabal umbraculifera* (Jacq.) Martius, *Trachycarpus fortunei* (Hook), *Washingtonia filifera* (L. Lindl), *W. robusta* H. Wendl. and *Syagrus romanzoffiana* (Cham.). The non-palm hosts are the century plant *Agave americana* and sugarcane *Saccharum officinarum* [9].

Considering such a wide host range of this pest, it is imperative to ensure proper phytosanitary measures are in place before palms are transported/shipped. Recently, FAO has published the detailed guidelines on phytosanitary regulations to be adopted to ensure the movement of RPW free planting material within national borders and from one country to another [11]. Import and movement of infested plant material within a country are the main pathways to the introduction and spread of *R. ferrugineus*. Short-distance spread is possible by adult flight. The pest can be spread over long distances in infested palms for planting of host palms [7]. Flight mill studies have demonstrated that RPW being a sizeable population is short-distance fliers (<100 m) which would explain the aggregated/clumped distribution of infestation. RPW has the capacity to fly up to 50 km in a day with flight activity being predominantly diurnal [12–14].

### **4. Biology and symptoms of damage**

Understanding the biology of the pest is essential in developing, implementing and sustaining management practices. RPW is a hidden pest, with all its life stages developing inside the palm except for the adult stage, which is partly exposed when adult weevils fly out of the brood in search of the host or on occasions to find a mate.

Recently, Al-Ayedh [15] in the FAO guidelines on RPW management and EPPO [7], using RPW data sheets, has summarized the literature on the biology of this pest.

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

There are several previous reports on the biology of RPW on natural and artificial diets [8, 16–23]. **Figure 2** depicts the life stages with the probable duration of each stage.

RPW takes about 3–4 months to complete its life cycle. Volatiles released from fresh wounds/cuts on the palm helps in egg laying by attracting adult RPW female weevils. Gravid females lay eggs in cracks and crevices on soft palm tissue. In coconut and date palm, oviposition usually occurs in young palms below 20 years old. There is a weak relationship between *Oryctes* sp. infestations and RPW attack in coconut and date palm [24, 25]. An adult female lays over 200 eggs. Oviposition is strongly affected by temperature [22]. On hatching, the legless larvae start feeding and move towards the interior of the palm. In areas with a mean annual temperature (MAT) below 15°C, one generation per year can be expected, while more than two generations in those with MAT above 19°C. Several overlapping generations of the pest may occur inside a single infested palm. Further, in the Mediterranean region, the larval stage can get prolonged up to 160 days in winter-spring seasons [22]. Upon completion of the larval period (7–16 instars), mature larvae pupate in cylindrical fibrous cocoons, leading to the emergence of adult weevils (**Figure 2**). When RPW was reared in the laboratory on a meridic diet, some of the larvae successfully pupate and develop to adults without construction of cocoons (**Figure 3**) (El-Shafie, unpublished data).

Date palms below the age of 20 are more susceptible to attach by RPW. Infestation is found more common on the trunk within 1 m from the ground; however, infestation can occurs on aerial offshoots and the crown of male palms [26]. Damage symptoms on Date palm (*Phoenix dactylifera*) have been described in detail [26–28]. The main symptoms include the following:

i.Oozing of brownish viscous fluid together with frass (palm tissue excreted by feeding grubs) which has a typical fermented odour

ii.Drying of outer leaves and fruit bunches and drying of infested offshoots

#### **Figure 2.**

*Schematic Diagram Depicting the Life Cycle of RPW (Source: Faleiro and Al-Shawaf 2018; http://hdl.handle. net/20.500.11766/8914).*

**7**

**Figure 4.**

**Figure 3.**

*El-Shafie).*

*Red Palm Weevil* Rhynchophorus ferrugineus *(Coleoptera: Curculionidae): Global Invasion…*

iv.Presence of adults and pupae at the base of the fronds and on the ground

iii.Topping of the trunk in case of severe and extensive tissue damage

*Successful emergence of a viable RPW adult from a pupa without fibrous cocoon (Photo: Hamadttu A. F.* 

*Drying or withering of aerial offshoots, the fronds of which can be easily pulled out (left). Oozing out of brown* 

*viscous unpleasant liquid from wounds in the trunk (right) (Photo: Hamadttu A. F. El-Shafie).*

*DOI: http://dx.doi.org/10.5772/intechopen.93391*

near infested palms

*Red Palm Weevil* Rhynchophorus ferrugineus *(Coleoptera: Curculionidae): Global Invasion… DOI: http://dx.doi.org/10.5772/intechopen.93391*


#### **Figure 3.**

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

without construction of cocoons (**Figure 3**) (El-Shafie, unpublished data). Date palms below the age of 20 are more susceptible to attach by RPW. Infestation is found more common on the trunk within 1 m from the ground; however, infestation can occurs on aerial offshoots and the crown of male palms [26]. Damage symptoms on Date palm (*Phoenix dactylifera*) have been described in detail

by feeding grubs) which has a typical fermented odour

i.Oozing of brownish viscous fluid together with frass (palm tissue excreted

ii.Drying of outer leaves and fruit bunches and drying of infested offshoots

*Schematic Diagram Depicting the Life Cycle of RPW (Source: Faleiro and Al-Shawaf 2018; http://hdl.handle.*

[26–28]. The main symptoms include the following:

There are several previous reports on the biology of RPW on natural and artificial diets [8, 16–23]. **Figure 2** depicts the life stages with the probable duration of each stage. RPW takes about 3–4 months to complete its life cycle. Volatiles released from fresh wounds/cuts on the palm helps in egg laying by attracting adult RPW female weevils. Gravid females lay eggs in cracks and crevices on soft palm tissue. In coconut and date palm, oviposition usually occurs in young palms below 20 years old. There is a weak relationship between *Oryctes* sp. infestations and RPW attack in coconut and date palm [24, 25]. An adult female lays over 200 eggs. Oviposition is strongly affected by temperature [22]. On hatching, the legless larvae start feeding and move towards the interior of the palm. In areas with a mean annual temperature (MAT) below 15°C, one generation per year can be expected, while more than two generations in those with MAT above 19°C. Several overlapping generations of the pest may occur inside a single infested palm. Further, in the Mediterranean region, the larval stage can get prolonged up to 160 days in winter-spring seasons [22]. Upon completion of the larval period (7–16 instars), mature larvae pupate in cylindrical fibrous cocoons, leading to the emergence of adult weevils (**Figure 2**). When RPW was reared in the laboratory on a meridic diet, some of the larvae successfully pupate and develop to adults

**6**

**Figure 2.**

*net/20.500.11766/8914).*

*Successful emergence of a viable RPW adult from a pupa without fibrous cocoon (Photo: Hamadttu A. F. El-Shafie).*

#### **Figure 4.**

*Drying or withering of aerial offshoots, the fronds of which can be easily pulled out (left). Oozing out of brown viscous unpleasant liquid from wounds in the trunk (right) (Photo: Hamadttu A. F. El-Shafie).*

#### **Figure 5.**

*Ejection of chewed-up fibers from the crown of an infested young date palm (left). Smashed internal palm tissue due to feeding of grubs (Photo: Hamadttu A. F. El-Shafie).*

Visual symptoms of damage on palms are used for early detection of RPW infestation. Thus, it is of paramount importance for field inspectors and palm growers to understand these symptoms (**Figures 4** and **5**). On Canary Island palm (*Phoenix canariensis*), infestation and damage occur in the crown. The larvae tunnel in the developing leaves (fronds) and severe infestation may lead to palm mortality. Early symptoms include the presence of holes in the fronds, which look chewed and broken. Wilting and drying of developed fronds and absence of new emerging fronds cause asymmetrical growth of the crown that later collapse. As is the case with date palm, different stages of the weevil can be seen at the crown particularly when infestation is more severe [29].
