PerspectivesAre you interested in submitting a Perspective Article? Be sure to read The Science Advisory Board's Editorial Guides for Perspective Articles. Click here. The Red Palm Weevil by Professor Aziz Ajlan Introduction: The red palm weevil (RPW), Rhynchophorus ferrugineus (Olivier) (Coleoptera: Curculionidae), is one of the dangerous pest of the date palm and 17 other palm species such as coconut, palm oil, sago, kentia palm (2009) in Palermo, Sicilia, Italy. First published information on RPW was in 1891 in India but in 1906, was described as a serious pest of the coconut palm, while in 1917 it was described as a serious pest of the date palm in the Punjab, India. However, RPW caused serious damage to the date palm in Mesopotamia (Iraq) in 1918, but no insect specimens were collected to confirm it. RPW was discovered during the mid-1980s in the Arabian Gulf countries and has become a seriously deadly pest of date palms in the Middle East.  However, date palm, Phoenix dactylifera L. (Palmales: Palmae), is one of the oldest fruit trees in the world and is mentioned in the Holy Books (Qurân and a Bible). There are 100 million date palms worldwide, approximately 62 million can be found in the Arab region. The origin of the date palm is unknown. However, some claim that the date palm first originated in Babel, Iraq, while others believe that it originated in Dareen or Hofuf, Saudi Arabia, or Harqan, an island on the Arabian Gulf in Bahrain. The date palm is a perennial, and lives to 150 years. Normally, the female date palm begins to bear dates within an average of 5 years from the time of the offshoot planting. The major date palm producing areas of the world are the Middle East and North Africa. Â  Distribution of Red Palm Weevil Currently, the distribution of RPW is global. In 2008 and 2009, the RPW is reported from Republic of Georgia, Caribbean (Curacao island/ Netherland Antilles) and Morocco. Also, RPW occurs in the following countries: Bahrain, Bangladesh, Burma, Cambodia, China, Cyprus, Egypt, France, Greece, India, Indonesia, Iran, Iraq, Israel, Italy and Sicily, Japan, Jordan, Kuwait, Laos, Myanmar, Oman, Pakistan, Palestine, Philippines, Qatar, Saudi Arabia, Singapore, Spain, Sri Lanka, Syria, Taiwan, Thailand, Turkey, United Arab Emirates, Vietnam, and in Oceania: Papua New Guinea, Solomon Islands, Western Samoa.  Life Cycle The life cycle is complete metamorphosis. All stages of RPW (egg, larva, pupa and adult) are spent inside the palm itself. Thus, the life cycle cannot be completed elsewhere. The females deposit about 300 eggs in separate holes or injuries on the palm. Eggs hatch in 2 to 5 days into legless larvae (grubs) which bore into the interior of the palms, moving by peristaltic muscular contractions of the body. The larvae feed on the soft succulent tissues, discarding all fibrous material. The larval period varies from 1 to 3 months and the larvae pupate in elongate oval cylindrical cocoons made out of fibrous strands. The pupation period lasts 14 to 21 days, the adult weevils emerge at the end. Thus, the life cycle takes about 4 months to be completed. Normally, RPW prefers to infest palms below the age of 20 years, where the stem of the young palm is soft, juicy and easy to penetrate. The larvae are responsible for damaging the palm, and once they have gained access, the death of the palm generally ensues. The larva normally never comes to the surface, since it begins its life inside the palm. Therefore, neither the damage nor the larva can be seen. However, the trunk of the palm can be infested in any parts, including the crown. The damage caused by a few larvae of the weevil is astonishing. Even one larva may cause considerable damage, and, sometimes the death of the palm. It is difficult to assess the actual loss caused by this pest, but undoubtedly it affects the production of date palms. All palms are probably suitable for the development of the RPW, which has been found on the following palms: Kentia palm (2009) in Palermo, Sicilia, Italy, Coconut palm, Date palm, Nigbong palm, Oil palm, Ornamental palm, Palmyra palm, Royal palm, Sago palm, Sedang palm, Sugar palm, Talipot palm, Wild date (toddy) palm.  Eggs The eggs are creamy white in color, long and oval in shape. The average size of an egg is 2.6 mm long and 1.1 mm wide. Larvae (grubs) The full-grown larvae are conical in shape and are legless fleshy grubs. They appear yellowish brown, while the newly hatched larvae are yellowish white in color, with brown heads. The length of the full-grown larva is 50 mm and the width is 20 mm. The head is brown in color and bent downwards. Mouthparts are well developed and strongly chitinized, which enables the grubs to burrow into the trunk. However, the grubs requires moist environment. Cocoons The grubs pupate in elongate oval, cylindrical cocoons made out of fibrous strands. When about to pupate, the larvae construct the cocoons, which are oval in shape, with an average length of 60 mm and a width of 30 mm. Pupae The pupae are first cream colored and later turn brown. The heads are bent ventrally, the rostrum reaching the tibiae of the first pair of legs. The antennae and eyes are quite prominent. The elytra and wings are brought down ventrally, passing underneath the femora and tibiae of the second pair of legs, overlapping the third pair of legs and meeting in the middle of the abdomen. The average length of the pupa is 35 mm and the width is 15 mm. Adults At the end of the 14 to 21-day pupation period, the adult weevils emerge and are reddish brown cylinder with a long prominent curved snout. They vary considerably in size and are about 35 mm in length and 12 mm in width. The head and rostrum comprise about one third of the total length. The mouthparts are elongated in the form of a slender snout or rostrum, which bears a small pair of biting jaws at the end and a pair of antennae near the base. The rostrum is reddish brown dorsally, and ventrally it is dark brown. In the male, the dorsal apical half of the snout is covered with a pad of short brownish hairs; the snout of the female is bare, more slender, curved and a little longer. The antennae consist of the scape and funicle. The eyes are black and separated on both sides of the base of the rostrum. The pronotum is reddish brown in color and has a few black spots. These black spots are variable in shape, size and number. The elytra are dark red, strongly ribbed longitudinally, and do not cover the abdomen completely. The wings are brown in color and the weevils are capable of strong flight. The male weevil has a tuft of soft reddish brown hairs along the dorsal aspect of the snout; this tuft is absent in the female. Also, the male produces an aggregation pheromone (4-methyl-5-nonanol), which is a synthetic lure used in the pheromone bucket traps. Economic Importance and Damage Normally, the red palm weevils infest palms below the age of 20 years, where the stem of the young palm is soft, juicy and easily penetrated. The weevils are destructive pests to palms. The larvae are responsible for damaging the palm, and once they have gained access, the death of the palm generally ensues. The larvae normally never come to the surface, since they begin life inside the palm. Therefore, neither the damage nor the larvae can be seen. However, the trunk of the palm can be infested in any part, including the crown. The damage caused by only a few larvae is astonishing. Even one larva may cause considerable damage for a young palm (offshoot). It is difficult to assess the actual loss caused by this pest, but undoubtedly it affects the production of date palms.  Methods of Control Integrated Pest Management (IPM) Because the red palm weevils are difficult to control with just one method, several combinations of control methods should be applied as follows: Plant Quarantine The transport of offshoots as planting material from infested areas can contribute to the spread of the pest. Strict quarantine at international and national levels should be applied. Cultural Control Field sanitation and cultural practices are some of the important components to prevent weevil infestation.
Mechanical Control Dead palms or palms beyond recovery should be split open to expose the different stages of the pest present inside. The debris, including the outer logs and the crowns, should be burned. Trapping Weevils Trapping and destroying the weevils is another method to control the pest population. Trapping also is used to detect the presence of the pest in the field and also to assess the population. The aggregation pheromone lure of red palm weevil is used to attract the weevils to the bucket traps which contain pieces of palm stem as food and a solution of insecticide. Â   Biological Control No effective biological agent has been found that can be employed for the biological control of the pest. Chemical Control The wounds produced on palms due to cultural practices as well as anther wounds are favorite sites of oviposition by the female weevils. Treatment of such wounds by soaking them with insecticides can be an effective way to prevent red palm weevil entry into palms. Once infestation is detected in a palm, curative control must be applied. If the infestation is in the crown, remove the affected and damaged portions and apply insecticide suspension. In case of infestation in the trunk, the infested part should be cleaned and plugged with a mixture of mud and insecticide. Several insecticides under laboratory and field conditions are tested in order to evaluate the best insecticide that will affect the different stages of the weevil. Training and Education The cooperation of the farmer is essential in order to successfully implement weevil management. For any large-scale pest management program to succeed, it is imperative that farmers cooperate and become involved at the operational level. This can be achieved by making farmers aware of the seriousness of the problem and training them in various IPM skills. References Ajlan AM, Abdulsalam KS (2000) Efficiency of some pheromone traps for controlling red palm weevil, Rhynchophorus ferrugineus (Olivier) (Coleoptera: Curculionidae), under Saudi Arabia conditions. Bull Ent Soc Egypt Econ Ser 27:109-120 Ajlan AM, Shawir MS, Abo-El-Saad M, Rezk MA, Abdulsalam KS (2000) Laboratory evaluation of certain organophosphorus insecticides against the red palm weevil, Rhynchophorus ferrugineus (Olivier). Sci. J King Faisal Univ. (Basic Appl. Sci.) 1:15-26 EPPO, Reporting Service. No. 3, 2009-03-01. 2009/051 - Rhynchophorus ferrugineus found on Howea forsteriana in Sicilia (IT). EPPO, Reporting Service. No. 1, 2009-01-01. 2009/001 - First record of Rhynchophorus ferrugineus in Morocco. 2009/002 - First record of Rhynchophorus ferrugineus in Curacao, Netherlands Antilles. Faleiro JR (2006) A review of the issues and management of the red palm weevil Rhynchophorus ferrugineus (Coleoptera: Rhynchophoridae) in coconut and date palm during the last one hundred years. Int J Trop Insect Sci 26:135-154 Hallett RH, Gries G, Borden JH, Czyzewska E, Oehlschlager AC, Pierce HD Jr, Angerilli NPD, Rauf A (1993) Aggregation pheromones of two Asian palm weevils, Rhynchophorus ferrugineus and R. vulneratus. Naturwissenschafen 80:328-331 Murphy ST, Briscoe BR (1999) The red palm weevil as an alien invasive: biology and the prospects for biological control as a component of IPM. Biocontrol News Inf 20:35N-46N Nirula KK (1956) Investigations on the pests of coconut palm. IV. Rhynchophorus ferrugineus F. Indian Coconut J 9:229-247 ### << Previous Next >> [ View All Perspectives ] |
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