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It is very difficult to detect R. ferrugineus in the early stages of infestation. Generally, it is detected only after the palm has been severely damaged. Careful observation may reveal the following signs which are indicative of the presence of the pest (Coconut Research Institute, 1987):
- some holes in the crown or trunk from which chewed-up fibres are ejected. This may be accompanied by the oozing of brown viscous liquid
- crunching noise produced by the feeding grubs can be heard when the ear is placed to the trunk of the palm
- a withered bud/crown.
Integrated Pest Management Programmes
Integrated pest management for R. ferrugineus has been developed and tested in coconut palms in India (Kurian et al., 1976; Sathiamma et al., 1982, Abraham et al., 1989). Included in the IPM programme were cultural measures such as plant and field sanitation; physical methods by preventing entry of weevils through cut ends of petioles and wounds; and use of attractants and other chemicals (including filling of leaf axils with gamma BHC and sand as a preventive measure). Abraham et al. (1989) found the IPM approach very effective in reducing the number of infested palms in Kerala, India. Abraham et al. (1998) suggested that the major components of the IPM strategy for R. ferrugineus are surveillance, trapping the weevil using pheromones lures, detecting infestation by examination of palms, eliminating hidden breeding sites, clearing abandoned gardens, maintaining crop and field sanitation, using preventive chemical treatments, curative chemical control, implementing quarantine measures, training and education. In the Al Qatif region of Saudi Arabia, Vidyasagar et al. (2000a) successfully developed an IPM programme which, in addition to mass pheromone trapping, included a survey of all the cultivated gardens, systematic checking of all palms for infestation, periodic soaking of palms, and mass removal of neglected farms. A review of control strategies and IPM for the weevil were also presented by various other authors (Ramachandran, 1998; Nair et al., 1998; Murphy and Brisco, 1999). Faleiro (2006) has reviewed the issues and management of R. ferrugineus in coconut and date palm over the past 100 years.
Cultural and Sanitary Methods
These include prompt destruction of infested plant material (Kurian and Mathen, 1971) and prophylactic treatment of cut wounds (Pillai, 1987). Abraham (1971) suggested that leaves be cut at or beyond the region where leaflets emerge at the base to prevent entry by the weevil into the stem. Azam and Razvi (2001) found that deep cutting to completely remove the growing point of off-shoots (unwanted growths from the trunk), then treating the cut surface with an insecticide such as formothion or dimethoate and covering it with mud reduced the level of infestation to less than 4% compared to 20% for an untreated control (cut at the trunk surface).
Parasitoids and predators
There is not much information on the advocation of the classical approach for the use of biological control agents against R. ferrugineus. However, Reginald (1973) reported a fortuitous occurrence when Platymerus laevicollis was imported into Sri Lanka from Western Samoa as a possible predator on Oryctes rhinoceros and was found to prefer R. ferrugineus. There have also been studies to evaluate the potential of predators and parasites; Abraham and Kurian (1973) reported that Chelisoches morio nymphs consumed 5.3 weevil eggs and 4.2 weevil larvae per day whereas C. morio adults consumed 8.5 weevil eggs and 6.7 weevil larvae per day. In addition, they provided some information on the biology of this predator in the laboratory and field.
Abbas and Hononik (1999) found that Steinernema riobrave, S. carpocapsae and Heterorhabditis sp. were pathogenic to both larval and adult stages of R. ferrugineus in the laboratory. They also reported that propagation of the nematodes was possible in the adult but rare in the larvae. Laboratory studies conducted by Banu et al. (1998) showed that the larva of R. ferrugineus was host to the naturally-occurring entomopathogenic nematode Heterorhabditis indicus in Kerala, India. Salama and Abd-Elgawad (2001) baited using the greater wax moth larvae and obtained five strains of heterorhabditid nematodes, which were more virulent on R. ferrugineus than the other entomophilic nematode species in culture. However, only two of the strains survived a 24-h exposure period in palm-infested tree tissue. Hanounik (1998) reported that the application of genetically enhanced strains of Steinernema and Heterorhabditis to the larvae of R. ferrugineus resulted in 95-100% mortality in the laboratory and 50% mortality in the field. El Bishry et al. (2000) studied the impact of date palm tissues infested with R. ferrugineus on five entomopathogenic nematode strains in the laboratory. Results showed that juveniles of all strains were killed within 24 h when placed on infested tissues. The washings of these tissues also had a detrimental effect on the nematodes. The dispersal and host finding ability of three of the strains was negatively affected in palm tissues after washing and sterilization. For further information on the use of entomopathogenic nematodes against R. ferrugineus, see Monzer and Al-Elimi (2002), Saleh and Alheji (2003), Saleh et al. (2004), Llácer et al. (2009), Dembilio et al. (2010, 2011), Jacas et al. (2011), Tapia et al. (2011) and Triggiani and Tarasco (2011).
Dangar (1997) studied the potency of a free-living unidentified yeast isolated from the haemolymph of R. ferrugineus as a biocontrol agent. The LD50 and LT50 values for larvae were calculated to be 8,000,000 yeasts/insect and 4 days, respectively.
Other Control Measures
Laboratory tests in India showed that the oil derivative from garlic and its synthetic form diallyl disulphide were toxic to the weevil (Murthy and Amonkar, 1974).
Pheromones and other behavioural chemicals
Pheromones are increasingly being used as a management tool against R. ferrugineus. Detailed protocols for pheromone-based mass trapping of the weevil are provided by Hallett et al. (1999). Faleiro et al. (1999) evaluated pheromone lures for the weevil in date plantations in Saudi Arabia and found that high release lures (Ferrolure and Ferrolure+) obtained from Chem Tica Natural, Costa Rica, attracted twice as many weevils as low release formulations. These pheromone lures were equally effective in attracting the pest and were on a par with Agrisense lures from the UK. Vidyasagar et al. (2000b) measured the impact of using a pheromone-based mass trapping system as a component of IPM of the weevil in Saudi Arabia using aggregation pheromone, ferrugineol, 4-methyl-5-nonanol (Ferrolure) and/or 4-methyl-5-nonanol + 4-methyl-5-nonanone (9:1) (Ferrolure+). Adult weevil populations were reduced from 4.12 weevils per trap per week in 1994 to 2.02 weevils per trap per week in 1997 when this system was used and there was a significant reduction in the level of infestation of date palms by the weevil during this period. In terms of population dynamics, peak adult populations were trapped immediately after the winter season during April and May and a smaller peak was observed during October and November just before the onset of winter. There was a drop in captures of weevils at the onset of winter. El Garhy (1996) reported thresholds temperatures for weevil activity in the range of 12-14°C, with more adults captured in summer than in winter and twice as many females captured as males, irrespective of season. Faleiro et al. (1999) compared Ferrolure and Ferrolure+ and reported that the longevity of the lures was lower in summer than in winter. The longevity of both was greater under shade and when traps were exposed to sunlight; Ferrolure+ lasted longer than Ferrolure. Gunawardena et al. (1998) identified host attractants for the weevil from freshly cut coconut bark and found that a 1:1 mixture of gamma nonanoic lactone 1 and 4-hydroxy-3- methoxystyrene 2 were responsible. Perez et al. (1996) reported that there were no apparent differences between the pheromones of R. ferrugineus and R. vulneratus.
Sterile Backcrosses /Sterile Insect Technique /Chemosterilization
Ramachandran (1991) reported the effects of gamma radiation on R. ferrugineus whereby production of viable eggs decreased with increasing radiation dose, although there was no apparent effect on the F2 generation. Rahalker et al. (1973) reported that treatment of 1-2-day-old males of the weevil at a dose of 1.5 krad (15 Gy) resulted in 90% sterility with no adverse effect on survival. Treatment of higher doses increased sterility but reduced survival. A ratio of ten treated males to one normal one was needed for appreciable suppression of progeny production. Using chemosterilants Rahalkar et al. (1975) reported that treatment of male weevils with metepa or hempa did not result in a satisfactory level of sterility without adversely affecting their survival. However, metepa was more toxic than hempa.
Due to the variable regulations around (de-)registration of pesticides, we are for the moment not including any specific chemical control recommendations. For further information, we recommend you visit the following resources:
Infestations of red palm weevil have a tremendous impact, not only on the economic produce of the palm (dates) but also on society. In the Gulf region, date palm is closely associated with the culture, religion and the life of the people. Approximately 30% of the world’s date production comes from the Gulf region of the Middle-East. Recent statistics shows that red palm weevil infestation may cause severe economic losses ranging between 1 and 5%, accounting for 5.18 to 25.92 million USD, respectively, with indirect losses increasing this figure several fold. The estimated cost saving of the curative treatment of palms in the early stage of attack is US $20.73 to 103.66 million for 1 and 5% infestation levels, respectively (El-Sabea et al., 2009). Menon and Pandalai (1960) suggested that R. ferrugineus is a serious pest of coconut palms in India and Sri Lanka. Ganapathy et al. (1992) observed R. ferrugineus damage in 34% of coconut groves in Cochin, India. Dhileepan (1991) reported that the weevil is a major pest of oil palms in Kerala. Flach (1983) suggested that R. ferrugineus and R. vulneratus are major pests of the sago palm in Sarawak. A relatively recent record of R. ferrugineus in India as a pest on oil palm (Misra, 1998) poses serious implications to some countries in South-East Asia (e.g. Malaysia, Indonesia) where oil palm is a major economic crop. In most European countries, the target of red palm weevil infestation is mainly the ornamental palms ruining the aesthetic beauty of parks and roads. Overall, red palm weevil damage to any type of palm accounts for losses of millions of dollars because the pest feeds on the trunk.