**5.9 Biological control**

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

In perineal crops, such as palms, farmers prefer to cultivate commercial cultivars that are well established and popular in the area/region. These cultivars/ varieties are often the most susceptible to RPW. Host plant resistance has not been fully studied and exploited with regard to RPW in spite of some preliminary research that has characterized palm cultivars in terms of tolerance/susceptibility to RPW [20, 85, 86]. The screening techniques to identify resistant RPW cultivars and parental material for use in breeding programmes need to be developed. The molecular markers-assisted breeding programme for the development of RPW resistant cultivars is another avenue that could be pursued. Advanced molecular techniques such as RNAi could hasten the utilization of host plant resistance

Palm density, irrigation methods and protection of tissue immediately after the frond and offshoot removal are probably the most important agro-techniques

Traditional date palm plantations have palms planted at a close spacing, often restricting sunlight penetration resulting in the build up of in-groove humidity conducive for the development of RPW [90]. Dense planting coupled with flood irrigation and inadequate drainage accelerates the build up of in-groove humidity. In this context, it is recommended to plant new plantations at the recommended

In flood-irrigated palms, often, the water touches the trunk at the ground, which

encourages adult weevils to oviposit in the collar region of such palms, resulting in new infestations. It is therefore recommended that drip irrigation systems be installed as a precaution for RPW control [87]. Care should be taken to see that palms receive adequate irrigation water as the scarcity of water may result in the

Adult weevils are attracted to palm volatiles emitted from the fresh wounds of palm tissue after the frond and offshoot removal. This calls for the immediate treatment of wounds on the palm to mask the emitting palm volatiles and avoid the gravid female weevil getting attracted to these sites for oviposition. As a precaution, these pruning activities could be carried out during winter when temperatures are low which adversely impacts the egg hatch and larval development [22]. No oviposition

incidence of the date palm stem borer *Jebusaea hammerschmidti* [91].

are officially certified to propagate such materials should be imported.

ing the importance of adopting good agronomic practices.

**5.7 Palm resistance to RPW**

against RPW [70].

*5.8.1 Palm density*

**5.8 Agro-techniques and RPW management**

related to RPW management [87–89].

spacing to allow sunlight penetration.

*5.8.2 Impact of irrigation*

*5.8.3 Protecting fresh wounds*

was observed for females kept below 15°C [92].

As regards date palm, only those propagated in vitro in test tubes by laboratories that

The RPW-IPM strategy at *level-3* outlines the prospect of palm tolerance to RPW and encourages the use of biological control to combat the pest, besides emphasiz-

**16**

Biological control is an integral part of several sustainable IPM programmes the world over. Biocontrol could play a significant role in augmenting the existing pheromone-based RPW-IPM strategy. Conventional control measures against RPW such as mass pheromone trapping and chemical treatments for preventive and curative purposes have not given the desired level of control. A wide range of RPW natural enemies, viz. insects, bacteria, fungi, viruses, yeasts, entomopathogenic nematodes (EPN) and birds have been reported from several countries [26, 93]. Mazza et al. [94] enlisted more than 50 biological control agents against the *Rhynchophorus* group of weevils. Al-Deeb et al. [95] reported the presence of phoretic mites of the genera *Uropoda*, *Uroobovella* and *Curculanoetus* on RPW in UAE. Whether these mites cause a pathological effect on the weevil need to be investigated. In this respect, it has been found that an unidentified species of phoretic mite could cause high mortality among RPW pupae, as well as attenuation of adult weevils (El-Shafie, unpublished data) (**Figure 7**). Yasin et al. [96] reviewed the potential role of potential microbial agents in the control of RPW and concluded that strains of the fungi *Beauveria bassiana* and *Metarhizium anisoplia*e, isolated from naturally infected RPW, could contribute to biological control of this pest. There are several publications to show the efficacy of entomopathogenic nematodes (EPN) and the entomopathogenic fungi (EPF) in the laboratory and semi-field assays [96–101].

Laboratory and semi-field cage studies showed the possibility of infecting RPW adults with *B. bassiana* using pheromone traps [100]. Reports from Spain suggest that the EPN, *Steinernema* sp. [99], and the EPF, *B. bassiana* [102], are promising in the field. The role of parasitic tachinid flies from South America against the *Rhynchophorus* group of weevils could also be another potential avenue to explore [103, 104]. The current RPW-IPM programme could be significantly strengthened if the known biological control agents could be delivered to the target site and also sustained in the field.

At *level-4*, the strategy mainly visualizes capacity building, robust extension programmes to sensitize all stakeholders and farmer participation in the control programme.

### **5.10 Capacity building and extension programmes**

Building the capacity of farmers, home owners and officials is an essential component of the RPW control programme [37]. Dissemination of the latest information on RPW-IPM among all the stakeholders through the electronic and print media can go a long way in strengthening the area-wide RPW-IPM strategy.

#### **5.11 Farmer participation in RPW control**

In several countries, an extensive state support is provided while implementing the RPW-IPM programme, keeping the farmers' involvement either bare minimum or almost nil [37]. This makes it very difficult for the authorities to implement the programme. Closed farms, for example, often develop as breeding sites for RPW, diluting the success achieved in controlling the pest in the vicinity of such plantations/home grooves [27]. Farmers' participation and cooperation are vital for any IPM programmes to succeed [105]. Abdedaiem et al. [106] emphasized the need to take up socio-economic studies for better understanding and improving the farmers' involvement in the RPW control programme.

The spread of the pest in vast stretches of date plantations has resulted in outsourcing area-wide RPW-IPM programmes to private companies in some countries. This needs careful planning, implementation and supervision. Here, the lack of experienced staff to oversee operations in the field is a major constraint. Government authorities need to efficiently supervise, monitor and evaluate the control programme implemented by the private company, on a regular basis. Delay in providing necessary inputs (pheromones, insecticides, etc.) where the RPW control is entrusted to private agencies is another major concern. Often there is a delay in finalizing the tender/quotation for the subsequent period before the expiry of the on-going tender resulting in the stoppage of field operations. Any break in the control operations will result in the proliferation and spread of the pest.

## **6. Challenges of RPW management and future prospects**

As a prelude to the scientific consultation and high level meeting on RPW management held in Rome during March 2017, FAO prepared a base document ([1]; http://www.fao.org/3/a-ms664e.pdf) on the current situation of RPW in the NENA region where in the present management practices, challenges/weaknesses and available research and technologies for its improvement are outlined. There are several gaps and challenges in the core components of the current RPW-IPM strategy. The current RPW-IPM programmes based on pheromone trapping and other techniques have been implemented with limited success. Gaps and challenges in almost all the components of the strategy, particularly with regard to early detection of the pest, developing and implementing phytosanitary measures, limited efficacy of biological control agents in the field, lack of farmer participation in the programmes and scarcity of data on socio-economic issues among several other factors have made RPW control and eradication extremely difficult. On the positive side, the pest has been eradicated in the Canary Islands and is approaching eradication in Mauritania. Eradication has also been obtained in various oasis, but new introductions of infested palms have reversed the success achieved [2].

At level-1 of the strategy, the main challenge in early detection is to provide the farmer with a low cost and efficient detection device. There are several laboratories all over the world that have worked on advanced techniques such as detecting chemical signatures, acoustic detection, use of infrared cameras, thermal imaging,

**19**

needs adjustments.

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

satellite imaging/IoT, etc. [39–43]. Meanwhile, the visual inspection of palms to detect infested palms will continue to stay to detect RPW infested palms.

With regard to pheromone trapping, the need to regularly service the foodbaited traps to change the food bait, water and record weevil captures is cumbersome and is the main constraint. Trap and bait-free trapping (attract and kill) and dry trapping (Electrap™) have addressed the challenge to some extent although data collection on weevil captures continues to be a gap that needs to be addressed. Ideally a dry trap that automatically records and transmits weevil capture data is a prospect for the future. Besides attract and kill, other semiochemical mediated control methods against RPW such as 'push-pull', involving the use of repellents and attractants [107], and 'attract and infect', involving the spread of biological control agents (EPFs) using pheromone traps [100], needs to be refined and worked upon. As regards chemical treatments, there is an overdependence on the use of chemical insecticides for both preventive and curative treatments. Research on the efficacy of natural insecticides against RPW needs to be enhanced so that these can be encouraged and incorporated in the control strategy. It is observed that in well-managed plantations, the preventive insecticidal treatments on a regular calendar basis are not required. Furthermore, for curative treatments are pressure injectors really required? These are expensive and need to be operated under the supervision of trained personnel due to the possibility of rupturing the palm tissue leading to death of the palm if the pressure exceeds 2 bar. Instead the methodology for mechanical sanitization coupled with 'drill and inject' using the simple diffusion

The removal and safe disposal of severely infested palms is also another huge challenge. In several countries, this aspect of the strategy is constrained by the use of costly shredding machines that need trained personnel to operate. Besides, there is a danger of the weevils escaping during transportation of the eradicated palm to the shredder outside the farm to the shredding site. In this context, Ferry [74] recommends the processing/destruction of severely infested palms right at the farm itself. The possibility of using small portable shredders needs to be looked into.

Area-wide RPW-IPM programmes generate a huge amount of data that needs to be collected, processed and analysed. Periodic validation/performance analysis of the control programme is vital to have a grip of the situation and use the resources judiciously and is an important challenge that has to be met. Any meaningful validation of the control programme calls for meticulous record keeping, particularly of the weevil captures in the traps and the number and location of palms infested, palms treated and removed (eradicated). Record keeping is to be facilitated by having field maps of the operational areas wherein the position of the traps and infested palms can be plotted. Numbering of each trap in the field is vital in addition to geo-referencing all the traps and infestations reported. In the absence of professional GIS specialists in the programme, spatial and temporal spread sheets can be prepared periodically by plotting on the maps (use different colours) for weevil captures in traps and infested palms detected. High weevil captures or removal of too many infested palms indicates that the strategy is not doing well and

Systematic geographic information system (GIS)-linked data collection is indispensable, e.g., by using a large number of mapped (traps and weevil catches), the temporal as well as geographical changes in pest distribution can be monitored and infested palms detected by various means can be localized [41]. The future prospect for data collection, compiling and analysing in area-wide RPW-IPM programmes would be to develop and validate mobile apps for smartphones to record georeferenced data at the field location on a standard form. Recently, FAO has initiated the process to validate the SusaHamra app to assist farmers in better monitoring and

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

technique has to be standardized.

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

satellite imaging/IoT, etc. [39–43]. Meanwhile, the visual inspection of palms to detect infested palms will continue to stay to detect RPW infested palms.

With regard to pheromone trapping, the need to regularly service the foodbaited traps to change the food bait, water and record weevil captures is cumbersome and is the main constraint. Trap and bait-free trapping (attract and kill) and dry trapping (Electrap™) have addressed the challenge to some extent although data collection on weevil captures continues to be a gap that needs to be addressed. Ideally a dry trap that automatically records and transmits weevil capture data is a prospect for the future. Besides attract and kill, other semiochemical mediated control methods against RPW such as 'push-pull', involving the use of repellents and attractants [107], and 'attract and infect', involving the spread of biological control agents (EPFs) using pheromone traps [100], needs to be refined and worked upon.

As regards chemical treatments, there is an overdependence on the use of chemical insecticides for both preventive and curative treatments. Research on the efficacy of natural insecticides against RPW needs to be enhanced so that these can be encouraged and incorporated in the control strategy. It is observed that in well-managed plantations, the preventive insecticidal treatments on a regular calendar basis are not required. Furthermore, for curative treatments are pressure injectors really required? These are expensive and need to be operated under the supervision of trained personnel due to the possibility of rupturing the palm tissue leading to death of the palm if the pressure exceeds 2 bar. Instead the methodology for mechanical sanitization coupled with 'drill and inject' using the simple diffusion technique has to be standardized.

The removal and safe disposal of severely infested palms is also another huge challenge. In several countries, this aspect of the strategy is constrained by the use of costly shredding machines that need trained personnel to operate. Besides, there is a danger of the weevils escaping during transportation of the eradicated palm to the shredder outside the farm to the shredding site. In this context, Ferry [74] recommends the processing/destruction of severely infested palms right at the farm itself. The possibility of using small portable shredders needs to be looked into.

Area-wide RPW-IPM programmes generate a huge amount of data that needs to be collected, processed and analysed. Periodic validation/performance analysis of the control programme is vital to have a grip of the situation and use the resources judiciously and is an important challenge that has to be met. Any meaningful validation of the control programme calls for meticulous record keeping, particularly of the weevil captures in the traps and the number and location of palms infested, palms treated and removed (eradicated). Record keeping is to be facilitated by having field maps of the operational areas wherein the position of the traps and infested palms can be plotted. Numbering of each trap in the field is vital in addition to geo-referencing all the traps and infestations reported. In the absence of professional GIS specialists in the programme, spatial and temporal spread sheets can be prepared periodically by plotting on the maps (use different colours) for weevil captures in traps and infested palms detected. High weevil captures or removal of too many infested palms indicates that the strategy is not doing well and needs adjustments.

Systematic geographic information system (GIS)-linked data collection is indispensable, e.g., by using a large number of mapped (traps and weevil catches), the temporal as well as geographical changes in pest distribution can be monitored and infested palms detected by various means can be localized [41]. The future prospect for data collection, compiling and analysing in area-wide RPW-IPM programmes would be to develop and validate mobile apps for smartphones to record georeferenced data at the field location on a standard form. Recently, FAO has initiated the process to validate the SusaHamra app to assist farmers in better monitoring and

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

Building the capacity of farmers, home owners and officials is an essential component of the RPW control programme [37]. Dissemination of the latest information on RPW-IPM among all the stakeholders through the electronic and print media can go a long way in strengthening the area-wide RPW-IPM strategy.

In several countries, an extensive state support is provided while implementing the RPW-IPM programme, keeping the farmers' involvement either bare minimum or almost nil [37]. This makes it very difficult for the authorities to implement the programme. Closed farms, for example, often develop as breeding sites for RPW, diluting the success achieved in controlling the pest in the vicinity of such plantations/home grooves [27]. Farmers' participation and cooperation are vital for any IPM programmes to succeed [105]. Abdedaiem et al. [106] emphasized the need to take up socio-economic studies for better understanding and improving the farmers'

The spread of the pest in vast stretches of date plantations has resulted in outsourcing area-wide RPW-IPM programmes to private companies in some countries. This needs careful planning, implementation and supervision. Here, the lack of experienced staff to oversee operations in the field is a major constraint. Government authorities need to efficiently supervise, monitor and evaluate the control programme implemented by the private company, on a regular basis. Delay in providing necessary inputs (pheromones, insecticides, etc.) where the RPW control is entrusted to private agencies is another major concern. Often there is a delay in finalizing the tender/quotation for the subsequent period before the expiry of the on-going tender resulting in the stoppage of field operations. Any break in the control operations will result in the proliferation and spread of the pest.

**6. Challenges of RPW management and future prospects**

introductions of infested palms have reversed the success achieved [2].

At level-1 of the strategy, the main challenge in early detection is to provide the farmer with a low cost and efficient detection device. There are several laboratories all over the world that have worked on advanced techniques such as detecting chemical signatures, acoustic detection, use of infrared cameras, thermal imaging,

As a prelude to the scientific consultation and high level meeting on RPW management held in Rome during March 2017, FAO prepared a base document ([1]; http://www.fao.org/3/a-ms664e.pdf) on the current situation of RPW in the NENA region where in the present management practices, challenges/weaknesses and available research and technologies for its improvement are outlined. There are several gaps and challenges in the core components of the current RPW-IPM strategy. The current RPW-IPM programmes based on pheromone trapping and other techniques have been implemented with limited success. Gaps and challenges in almost all the components of the strategy, particularly with regard to early detection of the pest, developing and implementing phytosanitary measures, limited efficacy of biological control agents in the field, lack of farmer participation in the programmes and scarcity of data on socio-economic issues among several other factors have made RPW control and eradication extremely difficult. On the positive side, the pest has been eradicated in the Canary Islands and is approaching eradication in Mauritania. Eradication has also been obtained in various oasis, but new

**5.10 Capacity building and extension programmes**

**5.11 Farmer participation in RPW control**

involvement in the RPW control programme.

**18**

managing the RPW. A global platform is being established for mapping field data and analytics for better decision-making.

At level-2 of the strategy, phytosanitation/quarantine is very important. The main gaps and challenges here are: (i) national/regional phytosanitary/quarantine regulations against RPW are not adequately implemented; (ii) treatment protocols to treat palms prior to transportation and also after arrival at destination are not consistent; (iii) implementation of the regulations is weak due to insufficient staff that is often not trained; and (iv) certified planting material is difficult to get [2, 37]. Recently, Chouibani [11] has addressed these concerns in the FAO guidelines on RPW management. Although chemical protocols available for quarantine purposes are available for date palm offshoots, the need to develop an effective treatment protocol to treat and sanitize large palms for ornamental gardening before transportation has to be addressed on priority. It is the responsibility of respective NPPOs to ensure implementation of the phytosanitary measures against RPW.

The lack of biological control agents against RPW that are field worthy is another major concern. Although there are known biological control agents for RPW, delivery to the target site inside the palm and sustainability of these agents needs to be addressed. Furthermore, the importance of adopting the best agrotechniques related to palm density, frond and offshoot removal and irrigation practices is underestimated. There is scope to conduct research on these aspects to quantify the relationship between these factors and the incidence and severity of RPW. Host plant resistance against RPW is also not very well understood and offers a whole new area of exploration where the traditional plant breeding techniques coupled with advanced molecular based breeding techniques could be used to induce resistance against RPW in the popular palm cultivars. The entire genome of the date palm cultivar 'Khalas' has been sequenced [108, 109]. This could facilitate the integration of genetic engineering techniques into date palm breeding programmes that provide mechanisms to overcome the current constraints to conventional breeding in date palm and help incorporate desirable traits of yield, quality and resistance to abiotic and biotic stresses in date palm [110].

In several countries, the RPW-IPM programme is implemented largely by the state where farmers' participation is minimum or none. This impedes the performance and success of the strategy. Mechanisms need to be devised to increase farmers' participation in RPW-IPM programmes. In this context, Abdedaiem et al., [106] emphasized the need to take up socio-economic studies for enhancing farmers' involvement in the RPW control programme.

During the last few years, there are several publications that have generated data on the cutting-edge molecular aspects of RPW involving RNAi, gene expression, etc. [111–114]. Results of these studies need to be exploited in a way that the control strategy stands to benefit from such basic research.

Faleiro et al. [2] report that in recent years, a large number of new RPW-IPM tools (detectors, surveillance drones, pesticides, palm injectors, semiochemicals, biological control agents, palm shredders, microwave treatment devices, etc.) are available in the market. These IPM tools need proper testing and validation at the national and regional levels so that only field worthy technologies that are not costly and easy to use are made available to the farmers.

### **7. Conclusions**

The red palm weevil remains to be the invasive key pest threatening palms survival around the world. International trading and transportation of infested planting material (palms) for plantations and landscape purposes are the main

**21**

**Author details**

current technologies.

**Acknowledgements**

Hamadttu Abdel Farag El-Shafie1

Kingdom of Saudi Arabia

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

introduction pathways into new non-invaded areas. Current management strategies against RPW depend on monitoring and mass trapping using pheromones, agronomic and phytosanitary measures and to some extent biological control. Capacity building and quarantine measures are also among the RPW-IPM components. Despite major global efforts to combat the weevil, many gaps and challenges, in management strategies, need to be addressed. Such challenges include early detection of infestation, optimization of pheromone-baited traps, removal of highly infested palms, overdependence on the use of insecticides and participation of farmers in the control efforts. Future prospects of RPW management may include validation of management programmes, testing of high-tech technologies for practical field application and the use of RNAi technology in management programmes. It can be concluded that managing RPW in the field is not an easy task but with adequate resources, appropriate interventions supported by good coordination, planning and financial resources, the pest can be effectively controlled with the

The authors acknowledge and appreciate the financial support of this work provided by the Date Palm Research Center of Excellence, King Faisal University,

through funding the research project number DPRC-9-2018.

\* and Jose Romeno Faleiro2

1 Date Palm Research Center of Excellence, King Faisal University, Al-Ahsa,

© 2020 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/ by/3.0), which permits unrestricted use, distribution, and reproduction in any medium,

2 Ex-Indian Council of Agricultural Research, Goa, India

\*Address all correspondence to: elshafie62@yahoo.com

provided the original work is properly cited.

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

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

introduction pathways into new non-invaded areas. Current management strategies against RPW depend on monitoring and mass trapping using pheromones, agronomic and phytosanitary measures and to some extent biological control. Capacity building and quarantine measures are also among the RPW-IPM components. Despite major global efforts to combat the weevil, many gaps and challenges, in management strategies, need to be addressed. Such challenges include early detection of infestation, optimization of pheromone-baited traps, removal of highly infested palms, overdependence on the use of insecticides and participation of farmers in the control efforts. Future prospects of RPW management may include validation of management programmes, testing of high-tech technologies for practical field application and the use of RNAi technology in management programmes. It can be concluded that managing RPW in the field is not an easy task but with adequate resources, appropriate interventions supported by good coordination, planning and financial resources, the pest can be effectively controlled with the current technologies.
