The red palm weevil, Rhynchophorus ferrugineus, is a species of snout beetle also known as the Asian palm weevil or sago palm weevil. The adult beetles are relatively large, ranging between two and five centimeters long, and are usually a rusty red colour - but many colour variants exist and have often been misidentified as different species (e.g., Rhynchophorus vulneratus;). Weevil larvae can excavate holes in the trunk of a palm trees up to a metre long, thereby weakening and eventually killing the host plant. As a result, the weevil is considered a major pest in palm plantations, including the coconut palm, date palm and oil palm. Originally from tropical Asia, the red palm weevil has spread to Africa and Europe, reaching the Mediterranean in the 1980s. It was first recorded in Spain in 1994, and in France in 2006. The weevil was first reported in the Americas on Curaçao in January 2009 and sighted the same year in Aruba. It was reported in the United States at Laguna Beach, CA late in 2010. In the European Union, there have been confirmed detections in Malta and Italy (Tuscany, Sicily and Campania), and there are suspect reports suggesting that it has established along the Mediterranean coast of France and Portugal. Researchers also suspect that it has established in Morocco, Algeria and other North African countries, but there remains no official confirmation.
This weevil usually infests palms younger than twelve years. While the adult causes some damage through feeding, it is the burrowing of the larva into the heart of the palm that can cause the greatest mortality of trees. The adult female lays approximately two hundred eggs on new growth in the crown of the palm, at the base of young leaves, or in open lesions on the plant. The egg hatches into a white, legless larva. The larva will feed on the soft fibres and terminal buds, tunnelling through the internal tissue of the tree for about a month. The larvae can occasionally grow to a length of six to seven inches. At pupation, the larva will leave the tree and form a cocoon built of dry palm fibers in leaf litter at the base of the tree. The total life cycle takes about 7–10 weeks.
After fertilization, the adult female can lay between 300 and 500 eggs. They lay in holes they produced while searching for food, or take advantage of the cracks or wounds in a recently cut palm. At oviposition, females bend upward and the tarsi are anchored to the tissue with the spines of the third pair of legs to push the ovipositor into the tough palm tissue. After laying, the female protects and secures the eggs with a secretion that rapidly hardens around the eggs. On average, females produce 210 eggs per clutch, most of which hatch over a period of 3 days. The eggs are white, cylindrical, glossy, oval shaped, and measure 1 to 2.5 mm. The back of these eggs possess special 'gill cover' structures that provide the developing insect with oxygen.
The neonate larvae are yellow-white, segmented, legless, and have a chitinous head capsule (characteristic for curculionids) that is a darker brown than the rest of the body. They have powerful horizontal conical jaws which they use to burrow from the axils of the leaves to the crown, where they feed voraciously. Upon completion of larval development, the larva will emerge from the trunk of the tree, and build a pupal case of fiber extracted from the galleries inside the palm. The larva will then undergo metamorphosis into an adult.
The adult insect is an excellent flier and is able to travel great distances. While they prefer to attack palms that are already infested or weakened by other stresses, they will colonize healthy palms.
The behaviour and bionomics of the red palm weevil have been investigated in the field. The biology and life history of the weevil have been investigated on five diets, including banana, sugarcane, squash fruit, apple, and palm crown. The rate of development showed great variation depending on the host used. Developmental time was shortest on palm crown, followed by banana, and then squash fruit and apple, and longest on sugarcane. Egg production was the highest on palm crown, being 338 ± 37.24 eggs/female followed by banana, squash fruit, and apple, and the lowest (117. ± 18.9 eggs/female) on sugarcane.
Studies show that this insect is attracted by ethyl acetate, 2-mehoxy.4.vinylphenol, gamma-nonanoic lactone, 4SSS-ferrugineol, 50H and 4me-9-5Kt.
Symptoms of infestation
The infestation of the pest can result in yellowing and wilting of palms, that may lead to the death of the affected plant. The crown wilts first, and lower leaves will follow, due to damage to vascular tissue. Major symptoms such as crown loss or leaf wilt are usually only visible long after the palm has become infested. Secondary infections of opportunistic bacteria and fungi may occur within damaged tissues, accelerating decline. By the time these external symptoms are observed, the damage is usually sufficient to kill the tree, and the infestation may have been present for six months or longer. In high-density infestations, sounds of the larvae burrowing and chewing can be heard by placing one's ear to the trunk of the palm. Recent research has been conducted using electronic listening devices or dogs trained to recognize the scent of weevils or palm decay to detect infestations at low densities earlier in the process.
The main control method is through the application of a systemic insecticide. Insecticide is usually applied through a funnel about 5 cm above the infested area of the trunk. The red palm weevil can be monitored using pheromone lures  bucket or pitfall traps, and alternative forms of control use field sanitation and mass trapping with traps baited with pheromone and plant derived semiochemicals. New alternative technologies using semiochemicals and bio insecticides are being developed to more effectively control this devastating pest of palm trees. One of them is a new formulation with insecticide and pheromone called SPLAT RPW that attracts the weevils to a point source and kills them. Another ecofriendly management technique is to drench the base of palm fronds with the entomopathogenic fungus Metarhizium anisopliae, or Beauveria bassiana. An Italian company has developed a microwave collar that can be used to sterilize individual trees.
As the weevil prefers to lay its eggs in softer tissues, avoiding mechanical damage to plants can help to reduce infestation. Tarring wounds after pruning a plant of dead or old leaves can also reduce the probability of infestation. The movement of plant material such as husks, dead leaves, or untreated coir from infested to uninfested areas is not recommended.
The red palm weevil is reported to attack 17 palm species worldwide. Although the weevil was first reported on coconut in Southeast Asia, it has gained a foothold on date palm over the last two decades in several Middle Eastern countries, and then expanded its range to Africa and Europe. This expansion has been due to the movement of infested planting material. In the Mediterranean region, the red palm weevil also severely damages Phoenix canariensis. Currently, the pest is reported in almost 15% of the global coconut-growing countries and in nearly 50% of the date palm-growing countries.
The list of known hosts includes: Areca catechu, Arenga pinnata, Borassus flabellifer, Caryota maxima, C. cumingii, Cocos nucifera (coconut palm), Corypha gebanga, C. elata, Elaeis guineensis, Livistona decipiens, Metroxylon sagu, Oreodoxa regia, Phoenix canariensis, P. dactylifera (date palm), P. sylvestris, Sabal umbraculifera, Trachycarpus fortunei, Washingtonia spp. Lab studies have reared the insect on diets of Agave americana and Saccharum officinarum, but these findings have not been observed in the wild. There is evidence that the weevil prefers the 'Sukkary' cultivar of date palm to other cultivars.
Bangladesh, Bahrain, Cambodia, China, India, Indonesia, Japan, Kuwait, Laos, Malaysia, Myanmar, Oman, Pakistan, Philippines, Qatar, Saudi Arabia, Sri Lanka, Taiwan, Thailand, United Arab Emirates and Vietnam, Egypt, also Papua-New Guinea and Solomon Islands. It has most recently been reported in Slovenia, France, Italy, Malta, Greece, Spain, Portugal, Turkey, Cyprus, Syria, Monaco, Morocco, Aruba and the United States.
The larval grub is considered a delicacy in much of Southeast Asia. "Sago Delight", or "Fried Sago Worms" are considered a speciality in Malaysia, although versions of this dish can be found in many Southeast Asian countries and Papua New Guinea, where it is regarded as a delicacy. Sago grubs have been described as creamy tasting when raw, and like bacon or meat when cooked. They are often prepared with sago flour. In New Guinea, sago worms are roasted on a spit to celebrate special occasions. They are eaten either raw or roasted, and are regarded as a special high-nutrient meal among most Sarawak tribes such as the Melanau and the Dayak. The Asmat, Korowai and Kombai peoples of southern New Guinea also hold the larva in high regard as a food source.
- Rhynchophorus ferrugineus at European and Mediterranean Plant Protection Organization (EPPO)
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- Rhynchophorus ferrugineus at North American Plant Protection Organization (NAPPO)
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